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	$41.76	4.342%	$43.5732	$43.57	$43.55	$43.60
Purchase #2	$86.72	10.383%	$95.7241	$95.72	$95.70	$95.70
Purchase #3	$220.52	10.322%	$243.2821	$243.28	$243.30	$243.30
Purchase #4	$152.46	6.871%	$162.9355	$162.94	$162.95	$162.90
Purchase #5	$177.28	11.625%	$197.8888	$197.89	$197.90	$197.90
Purchase #6	$152.44	4.594%	$159.4431	$159.44	$159.45	$159.40
Purchase #7	$159.62	8.820%	$173.6985	$173.70	$173.70	$173.70
7 purchase totals =	$990.80		$1,076.5453	$1,076.54	$1,076.55	$1,076.50