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	$41.88	3.669%	$43.4166	$43.42	$43.40	$43.40
Purchase #2	$79.32	13.197%	$89.7879	$89.79	$89.80	$89.80
Purchase #3	$122.51	12.480%	$137.7992	$137.80	$137.80	$137.80
Purchase #4	$61.48	4.278%	$64.1101	$64.11	$64.10	$64.10
Purchase #5	$184.55	11.145%	$205.1181	$205.12	$205.10	$205.10
Purchase #6	$130.33	6.173%	$138.3753	$138.38	$138.40	$138.40
Purchase #7	$33.82	3.328%	$34.9455	$34.95	$34.95	$34.90
7 purchase totals =	$653.89		$713.5527	$713.57	$713.55	$713.50