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	$98.27	11.593%	$109.6624	$109.66	$109.65	$109.70
Purchase #2	$164.65	9.245%	$179.8719	$179.87	$179.85	$179.90
Purchase #3	$19.61	11.118%	$21.7902	$21.79	$21.80	$21.80
Purchase #4	$213.32	13.681%	$242.5043	$242.50	$242.50	$242.50
Purchase #5	$100.29	8.409%	$108.7234	$108.72	$108.70	$108.70
Purchase #6	$89.75	5.793%	$94.9492	$94.95	$94.95	$94.90
Purchase #7	$45.59	3.830%	$47.3361	$47.34	$47.35	$47.30
7 purchase totals =	$731.48		$804.8375	$804.83	$804.80	$804.80