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	$222.44	5.345%	$234.3294	$234.33	$234.35	$234.30
Purchase #2	$146.29	12.496%	$164.5704	$164.57	$164.55	$164.60
Purchase #3	$129.64	11.668%	$144.7664	$144.77	$144.75	$144.80
Purchase #4	$100.86	9.618%	$110.5607	$110.56	$110.55	$110.60
Purchase #5	$160.50	3.243%	$165.705	$165.71	$165.70	$165.70
Purchase #6	$196.72	13.415%	$223.11	$223.11	$223.10	$223.10
Purchase #7	$37.66	10.806%	$41.7295	$41.73	$41.75	$41.70
7 purchase totals =	$994.11		$1,084.7714	$1,084.78	$1,084.75	$1,084.80