Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$189.28	10.501%	$209.1563	$209.16	$209.15	$209.20
Purchase #2	$111.37	12.712%	$125.5274	$125.53	$125.55	$125.50
Purchase #3	$230.29	4.596%	$240.8741	$240.87	$240.85	$240.90
Purchase #4	$159.42	13.465%	$180.8859	$180.89	$180.90	$180.90
Purchase #5	$114.79	11.346%	$127.8141	$127.81	$127.80	$127.80
Purchase #6	$200.63	12.318%	$225.3436	$225.34	$225.35	$225.30
Purchase #7	$178.39	7.730%	$192.1795	$192.18	$192.20	$192.20
7 purchase totals =	$1,184.17		$1,301.7809	$1,301.78	$1,301.80	$1,301.80