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	$147.63	3.283%	$152.4767	$152.48	$152.50	$152.50
Purchase #2	$31.86	4.425%	$33.2698	$33.27	$33.25	$33.30
Purchase #3	$193.66	11.683%	$216.2853	$216.29	$216.30	$216.30
Purchase #4	$139.49	9.513%	$152.7597	$152.76	$152.75	$152.80
Purchase #5	$43.70	8.829%	$47.5583	$47.56	$47.55	$47.60
Purchase #6	$216.82	4.464%	$226.4988	$226.50	$226.50	$226.50
Purchase #7	$152.72	9.802%	$167.6896	$167.69	$167.70	$167.70
7 purchase totals =	$925.88		$996.5382	$996.55	$996.55	$996.70