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	$143.35	6.344%	$152.4441	$152.44	$152.45	$152.40
Purchase #2	$183.49	11.260%	$204.151	$204.15	$204.15	$204.20
Purchase #3	$125.95	12.456%	$141.6383	$141.64	$141.65	$141.60
Purchase #4	$246.62	11.663%	$275.3833	$275.38	$275.40	$275.40
Purchase #5	$173.76	13.304%	$196.877	$196.88	$196.90	$196.90
Purchase #6	$72.89	10.552%	$80.5814	$80.58	$80.60	$80.60
Purchase #7	$124.57	7.465%	$133.8692	$133.87	$133.85	$133.90
7 purchase totals =	$1,070.63		$1,184.9443	$1,184.94	$1,185.00	$1,185.00