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	$203.75	8.345%	$220.7529	$220.75	$220.75	$220.80
Purchase #2	$112.40	3.297%	$116.1058	$116.11	$116.10	$116.10
Purchase #3	$133.62	9.453%	$146.2511	$146.25	$146.25	$146.30
Purchase #4	$154.63	7.705%	$166.5442	$166.54	$166.55	$166.50
Purchase #5	$245.26	10.610%	$271.2821	$271.28	$271.30	$271.30
Purchase #6	$59.76	3.527%	$61.8677	$61.87	$61.85	$61.90
Purchase #7	$196.92	10.498%	$217.5927	$217.59	$217.60	$217.60
7 purchase totals =	$1,106.34		$1,200.3965	$1,200.39	$1,200.40	$1,200.50