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	$204.52	5.431%	$215.6275	$215.63	$215.65	$215.60
Purchase #2	$131.87	7.137%	$141.2816	$141.28	$141.30	$141.30
Purchase #3	$246.41	11.864%	$275.6441	$275.64	$275.65	$275.60
Purchase #4	$19.75	5.385%	$20.8135	$20.81	$20.80	$20.80
Purchase #5	$179.83	13.127%	$203.4363	$203.44	$203.45	$203.40
Purchase #6	$62.28	7.402%	$66.89	$66.89	$66.90	$66.90
Purchase #7	$50.99	10.761%	$56.477	$56.48	$56.50	$56.50
7 purchase totals =	$895.65		$980.1700	$980.17	$980.25	$980.10