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	$170.49	8.194%	$184.46	$184.46	$184.45	$184.50
Purchase #2	$168.58	6.609%	$179.7215	$179.72	$179.70	$179.70
Purchase #3	$189.51	3.655%	$196.4366	$196.44	$196.45	$196.40
Purchase #4	$6.45	7.453%	$6.9307	$6.93	$6.95	$6.90
Purchase #5	$55.28	11.669%	$61.7306	$61.73	$61.75	$61.70
Purchase #6	$185.53	7.869%	$200.1294	$200.13	$200.15	$200.10
Purchase #7	$226.97	12.259%	$254.7943	$254.79	$254.80	$254.80
7 purchase totals =	$1,002.81		$1,084.2031	$1,084.20	$1,084.25	$1,084.10