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	$73.29	13.366%	$83.0859	$83.09	$83.10	$83.10
Purchase #2	$244.80	4.439%	$255.6667	$255.67	$255.65	$255.70
Purchase #3	$95.52	8.179%	$103.3326	$103.33	$103.35	$103.30
Purchase #4	$231.36	5.237%	$243.4763	$243.48	$243.50	$243.50
Purchase #5	$120.88	6.264%	$128.4519	$128.45	$128.45	$128.50
Purchase #6	$232.40	9.774%	$255.1148	$255.11	$255.10	$255.10
Purchase #7	$71.48	10.837%	$79.2263	$79.23	$79.25	$79.20
7 purchase totals =	$1,069.73		$1,148.3545	$1,148.36	$1,148.40	$1,148.40