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	$151.35	6.134%	$160.6338	$160.63	$160.65	$160.60
Purchase #2	$155.68	6.317%	$165.5143	$165.51	$165.50	$165.50
Purchase #3	$150.70	9.451%	$164.9427	$164.94	$164.95	$164.90
Purchase #4	$200.66	8.327%	$217.369	$217.37	$217.35	$217.40
Purchase #5	$115.81	10.317%	$127.7581	$127.76	$127.75	$127.80
Purchase #6	$148.67	5.135%	$156.3042	$156.30	$156.30	$156.30
Purchase #7	$107.93	10.486%	$119.2475	$119.25	$119.25	$119.20
7 purchase totals =	$1,030.80		$1,111.7696	$1,111.76	$1,111.75	$1,111.70