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	$89.63	7.508%	$96.3594	$96.36	$96.35	$96.40
Purchase #2	$137.56	10.654%	$152.2156	$152.22	$152.20	$152.20
Purchase #3	$145.53	13.762%	$165.5578	$165.56	$165.55	$165.60
Purchase #4	$110.41	12.702%	$124.4343	$124.43	$124.45	$124.40
Purchase #5	$210.97	7.829%	$227.4868	$227.49	$227.50	$227.50
Purchase #6	$248.94	8.322%	$269.6568	$269.66	$269.65	$269.70
Purchase #7	$19.49	3.364%	$20.1456	$20.15	$20.15	$20.10
7 purchase totals =	$962.53		$1,055.8563	$1,055.87	$1,055.85	$1,055.90