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	$8.25	4.630%	$8.632	$8.63	$8.65	$8.60
Purchase #2	$248.31	4.510%	$259.5088	$259.51	$259.50	$259.50
Purchase #3	$52.33	13.277%	$59.2779	$59.28	$59.30	$59.30
Purchase #4	$221.97	4.181%	$231.2506	$231.25	$231.25	$231.30
Purchase #5	$112.29	11.161%	$124.8227	$124.82	$124.80	$124.80
Purchase #6	$75.41	3.289%	$77.8902	$77.89	$77.90	$77.90
Purchase #7	$56.33	3.454%	$58.2756	$58.28	$58.30	$58.30
7 purchase totals =	$774.89		$819.6578	$819.66	$819.70	$819.70