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	$86.33	6.301%	$91.7697	$91.77	$91.75	$91.80
Purchase #2	$158.91	13.537%	$180.4216	$180.42	$180.40	$180.40
Purchase #3	$115.75	10.161%	$127.5114	$127.51	$127.50	$127.50
Purchase #4	$208.70	13.371%	$236.6053	$236.61	$236.60	$236.60
Purchase #5	$239.32	4.533%	$250.1684	$250.17	$250.15	$250.20
Purchase #6	$102.83	10.238%	$113.3577	$113.36	$113.35	$113.40
Purchase #7	$44.85	12.658%	$50.5271	$50.53	$50.55	$50.50
7 purchase totals =	$956.69		$1,050.3612	$1,050.37	$1,050.30	$1,050.40