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	$126.65	8.776%	$137.7648	$137.76	$137.75	$137.80
Purchase #2	$158.90	9.517%	$174.0225	$174.02	$174.00	$174.00
Purchase #3	$123.78	4.274%	$129.0704	$129.07	$129.05	$129.10
Purchase #4	$48.69	13.308%	$55.1697	$55.17	$55.15	$55.20
Purchase #5	$170.70	12.149%	$191.4383	$191.44	$191.45	$191.40
Purchase #6	$235.25	8.414%	$255.0439	$255.04	$255.05	$255.00
Purchase #7	$59.44	11.813%	$66.4616	$66.46	$66.45	$66.50
7 purchase totals =	$923.41		$1,008.9712	$1,008.96	$1,008.90	$1,009.00