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	$224.82	10.688%	$248.8488	$248.85	$248.85	$248.80
Purchase #2	$68.89	7.402%	$73.9892	$73.99	$74.00	$74.00
Purchase #3	$54.76	12.124%	$61.3991	$61.40	$61.40	$61.40
Purchase #4	$141.76	4.497%	$148.1349	$148.13	$148.15	$148.10
Purchase #5	$66.54	7.236%	$71.3548	$71.35	$71.35	$71.40
Purchase #6	$211.31	5.508%	$222.949	$222.95	$222.95	$222.90
Purchase #7	$101.87	9.593%	$111.6424	$111.64	$111.65	$111.60
7 purchase totals =	$869.95		$938.3182	$938.31	$938.35	$938.20