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	$68.52	4.686%	$71.7308	$71.73	$71.75	$71.70
Purchase #2	$84.85	6.671%	$90.5103	$90.51	$90.50	$90.50
Purchase #3	$223.68	3.764%	$232.0993	$232.10	$232.10	$232.10
Purchase #4	$92.94	12.315%	$104.3856	$104.39	$104.40	$104.40
Purchase #5	$224.76	8.312%	$243.4421	$243.44	$243.45	$243.40
Purchase #6	$169.82	9.204%	$185.4502	$185.45	$185.45	$185.50
Purchase #7	$30.45	7.401%	$32.7036	$32.70	$32.70	$32.70
7 purchase totals =	$895.02		$960.3219	$960.32	$960.35	$960.30