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	$170.79	8.279%	$184.9297	$184.93	$184.95	$184.90
Purchase #2	$111.96	7.571%	$120.4365	$120.44	$120.45	$120.40
Purchase #3	$134.31	13.681%	$152.685	$152.69	$152.70	$152.70
Purchase #4	$203.37	8.596%	$220.8517	$220.85	$220.85	$220.90
Purchase #5	$165.55	12.795%	$186.7321	$186.73	$186.75	$186.70
Purchase #6	$124.29	13.579%	$141.1673	$141.17	$141.15	$141.20
Purchase #7	$155.61	10.852%	$172.4968	$172.50	$172.50	$172.50
7 purchase totals =	$1,065.88		$1,179.2991	$1,179.31	$1,179.35	$1,179.30