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	$212.55	11.370%	$236.7169	$236.72	$236.70	$236.70
Purchase #2	$30.69	9.201%	$33.5138	$33.51	$33.50	$33.50
Purchase #3	$222.83	12.192%	$249.9974	$250.00	$250.00	$250.00
Purchase #4	$130.35	9.388%	$142.5873	$142.59	$142.60	$142.60
Purchase #5	$47.27	7.368%	$50.7529	$50.75	$50.75	$50.80
Purchase #6	$184.40	7.469%	$198.1728	$198.17	$198.15	$198.20
Purchase #7	$98.76	7.201%	$105.8717	$105.87	$105.85	$105.90
7 purchase totals =	$926.85		$1,017.6128	$1,017.61	$1,017.55	$1,017.70