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	$130.65	5.198%	$137.4412	$137.44	$137.45	$137.40
Purchase #2	$137.52	12.700%	$154.985	$154.99	$155.00	$155.00
Purchase #3	$150.44	8.242%	$162.8393	$162.84	$162.85	$162.80
Purchase #4	$136.34	8.613%	$148.083	$148.08	$148.10	$148.10
Purchase #5	$205.52	11.730%	$229.6275	$229.63	$229.65	$229.60
Purchase #6	$32.36	3.106%	$33.3651	$33.37	$33.35	$33.40
Purchase #7	$139.29	8.315%	$150.872	$150.87	$150.85	$150.90
7 purchase totals =	$932.12		$1,017.2131	$1,017.22	$1,017.25	$1,017.20