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	$59.35	4.409%	$61.9667	$61.97	$61.95	$62.00
Purchase #2	$235.72	12.684%	$265.6187	$265.62	$265.60	$265.60
Purchase #3	$226.60	7.869%	$244.4312	$244.43	$244.45	$244.40
Purchase #4	$130.49	11.504%	$145.5016	$145.50	$145.50	$145.50
Purchase #5	$38.90	3.213%	$40.1499	$40.15	$40.15	$40.10
Purchase #6	$80.62	3.487%	$83.4312	$83.43	$83.45	$83.40
Purchase #7	$57.70	3.764%	$59.8718	$59.87	$59.85	$59.90
7 purchase totals =	$829.38		$900.9711	$900.97	$900.95	$900.90