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	$186.86	11.526%	$208.3975	$208.40	$208.40	$208.40
Purchase #2	$127.57	9.665%	$139.8996	$139.90	$139.90	$139.90
Purchase #3	$67.63	10.632%	$74.8204	$74.82	$74.80	$74.80
Purchase #4	$54.72	11.131%	$60.8109	$60.81	$60.80	$60.80
Purchase #5	$142.42	9.374%	$155.7705	$155.77	$155.75	$155.80
Purchase #6	$143.44	3.416%	$148.3399	$148.34	$148.35	$148.30
Purchase #7	$239.59	7.805%	$258.29	$258.29	$258.30	$258.30
7 purchase totals =	$962.23		$1,046.3288	$1,046.33	$1,046.30	$1,046.30