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	$108.38	9.478%	$118.6523	$118.65	$118.65	$118.70
Purchase #2	$228.78	6.762%	$244.2501	$244.25	$244.25	$244.30
Purchase #3	$108.78	6.483%	$115.8322	$115.83	$115.85	$115.80
Purchase #4	$206.82	9.433%	$226.3293	$226.33	$226.35	$226.30
Purchase #5	$62.27	7.865%	$67.1675	$67.17	$67.15	$67.20
Purchase #6	$141.62	7.487%	$152.2231	$152.22	$152.20	$152.20
Purchase #7	$102.81	8.344%	$111.3885	$111.39	$111.40	$111.40
7 purchase totals =	$959.46		$1,035.8430	$1,035.84	$1,035.85	$1,035.90