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	$178.75	10.587%	$197.6743	$197.67	$197.65	$197.70
Purchase #2	$78.89	13.623%	$89.6372	$89.64	$89.65	$89.60
Purchase #3	$249.95	11.615%	$278.9817	$278.98	$279.00	$279.00
Purchase #4	$217.35	5.519%	$229.3455	$229.35	$229.35	$229.30
Purchase #5	$88.76	13.110%	$100.3964	$100.40	$100.40	$100.40
Purchase #6	$35.89	12.127%	$40.2424	$40.24	$40.25	$40.20
Purchase #7	$200.77	10.659%	$222.1701	$222.17	$222.15	$222.20
7 purchase totals =	$1,050.36		$1,158.4476	$1,158.45	$1,158.45	$1,158.40