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	$175.44	11.778%	$196.1033	$196.10	$196.10	$196.10
Purchase #2	$243.38	11.452%	$271.2519	$271.25	$271.25	$271.30
Purchase #3	$28.86	11.369%	$32.1411	$32.14	$32.15	$32.10
Purchase #4	$166.75	13.824%	$189.8015	$189.80	$189.80	$189.80
Purchase #5	$228.79	12.710%	$257.8692	$257.87	$257.85	$257.90
Purchase #6	$24.91	13.318%	$28.2275	$28.23	$28.25	$28.20
Purchase #7	$169.75	11.583%	$189.4121	$189.41	$189.40	$189.40
7 purchase totals =	$1,037.88		$1,164.8066	$1,164.80	$1,164.80	$1,164.80