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	$73.86	4.592%	$77.2517	$77.25	$77.25	$77.30
Purchase #2	$192.76	13.360%	$218.5127	$218.51	$218.50	$218.50
Purchase #3	$245.39	3.780%	$254.6657	$254.67	$254.65	$254.70
Purchase #4	$147.32	12.864%	$166.2712	$166.27	$166.25	$166.30
Purchase #5	$111.78	11.530%	$124.6682	$124.67	$124.65	$124.70
Purchase #6	$170.45	11.140%	$189.4381	$189.44	$189.45	$189.40
Purchase #7	$147.82	4.549%	$154.5443	$154.54	$154.55	$154.50
7 purchase totals =	$1,089.38		$1,185.3519	$1,185.35	$1,185.30	$1,185.40