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	$123.85	6.494%	$131.8928	$131.89	$131.90	$131.90
Purchase #2	$11.27	12.250%	$12.6506	$12.65	$12.65	$12.70
Purchase #3	$203.98	11.867%	$228.1863	$228.19	$228.20	$228.20
Purchase #4	$227.54	4.486%	$237.7474	$237.75	$237.75	$237.70
Purchase #5	$205.30	9.533%	$224.8712	$224.87	$224.85	$224.90
Purchase #6	$152.68	3.384%	$157.8467	$157.85	$157.85	$157.80
Purchase #7	$100.94	10.328%	$111.3651	$111.37	$111.35	$111.40
7 purchase totals =	$1,025.56		$1,104.5601	$1,104.57	$1,104.55	$1,104.60