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	$242.87	13.525%	$275.7182	$275.72	$275.70	$275.70
Purchase #2	$246.99	9.272%	$269.8909	$269.89	$269.90	$269.90
Purchase #3	$239.73	9.137%	$261.6341	$261.63	$261.65	$261.60
Purchase #4	$180.85	3.620%	$187.3968	$187.40	$187.40	$187.40
Purchase #5	$28.25	4.436%	$29.5032	$29.50	$29.50	$29.50
Purchase #6	$55.88	10.297%	$61.634	$61.63	$61.65	$61.60
Purchase #7	$40.35	4.760%	$42.2707	$42.27	$42.25	$42.30
7 purchase totals =	$1,034.92		$1,128.0479	$1,128.04	$1,128.05	$1,128.00