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	$179.34	3.829%	$186.2069	$186.21	$186.20	$186.20
Purchase #2	$106.33	7.689%	$114.5057	$114.51	$114.50	$114.50
Purchase #3	$50.89	8.152%	$55.0386	$55.04	$55.05	$55.00
Purchase #4	$167.48	9.406%	$183.2332	$183.23	$183.25	$183.20
Purchase #5	$168.47	6.667%	$179.7019	$179.70	$179.70	$179.70
Purchase #6	$57.53	7.223%	$61.6854	$61.69	$61.70	$61.70
Purchase #7	$161.88	6.462%	$172.3407	$172.34	$172.35	$172.30
7 purchase totals =	$891.92		$952.7124	$952.72	$952.75	$952.60