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	$196.85	12.723%	$221.8952	$221.90	$221.90	$221.90
Purchase #2	$149.91	4.164%	$156.1523	$156.15	$156.15	$156.20
Purchase #3	$146.45	3.564%	$151.6695	$151.67	$151.65	$151.70
Purchase #4	$176.62	9.682%	$193.7203	$193.72	$193.70	$193.70
Purchase #5	$188.31	4.443%	$196.6766	$196.68	$196.70	$196.70
Purchase #6	$40.49	12.790%	$45.6687	$45.67	$45.65	$45.70
Purchase #7	$242.43	11.702%	$270.7992	$270.80	$270.80	$270.80
7 purchase totals =	$1,141.06		$1,236.5818	$1,236.59	$1,236.55	$1,236.70