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	$175.63	12.105%	$196.89	$196.89	$196.90	$196.90
Purchase #2	$231.73	7.587%	$249.3114	$249.31	$249.30	$249.30
Purchase #3	$227.49	13.483%	$258.1625	$258.16	$258.15	$258.20
Purchase #4	$192.35	10.302%	$212.1659	$212.17	$212.15	$212.20
Purchase #5	$120.33	6.493%	$128.143	$128.14	$128.15	$128.10
Purchase #6	$206.97	7.754%	$223.0185	$223.02	$223.00	$223.00
Purchase #7	$199.59	3.645%	$206.8651	$206.87	$206.85	$206.90
7 purchase totals =	$1,354.09		$1,474.5564	$1,474.56	$1,474.50	$1,474.60