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	$110.98	5.388%	$116.9596	$116.96	$116.95	$117.00
Purchase #2	$249.40	10.478%	$275.5321	$275.53	$275.55	$275.50
Purchase #3	$81.53	6.642%	$86.9452	$86.95	$86.95	$86.90
Purchase #4	$106.98	3.733%	$110.9736	$110.97	$110.95	$111.00
Purchase #5	$101.61	3.662%	$105.331	$105.33	$105.35	$105.30
Purchase #6	$167.60	6.334%	$178.2158	$178.22	$178.20	$178.20
Purchase #7	$243.44	10.715%	$269.5246	$269.52	$269.50	$269.50
7 purchase totals =	$1,061.54		$1,143.4819	$1,143.48	$1,143.45	$1,143.40