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	$152.85	12.411%	$171.8202	$171.82	$171.80	$171.80
Purchase #2	$188.34	13.703%	$214.1482	$214.15	$214.15	$214.10
Purchase #3	$116.56	4.179%	$121.431	$121.43	$121.45	$121.40
Purchase #4	$214.59	13.655%	$243.8923	$243.89	$243.90	$243.90
Purchase #5	$196.87	6.816%	$210.2887	$210.29	$210.30	$210.30
Purchase #6	$233.38	6.327%	$248.146	$248.15	$248.15	$248.10
Purchase #7	$17.77	11.745%	$19.8571	$19.86	$19.85	$19.90
7 purchase totals =	$1,120.36		$1,229.5835	$1,229.59	$1,229.60	$1,229.50