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	$49.97	4.364%	$52.1507	$52.15	$52.15	$52.20
Purchase #2	$247.35	12.368%	$277.9422	$277.94	$277.95	$277.90
Purchase #3	$106.74	4.482%	$111.5241	$111.52	$111.50	$111.50
Purchase #4	$78.46	13.306%	$88.8999	$88.90	$88.90	$88.90
Purchase #5	$94.29	8.536%	$102.3386	$102.34	$102.35	$102.30
Purchase #6	$221.67	11.691%	$247.5854	$247.59	$247.60	$247.60
Purchase #7	$215.88	6.221%	$229.3099	$229.31	$229.30	$229.30
7 purchase totals =	$1,014.36		$1,109.7508	$1,109.75	$1,109.75	$1,109.70