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	$81.31	10.358%	$89.7321	$89.73	$89.75	$89.70
Purchase #2	$185.86	8.281%	$201.2511	$201.25	$201.25	$201.30
Purchase #3	$145.58	4.716%	$152.4456	$152.45	$152.45	$152.40
Purchase #4	$38.91	9.134%	$42.464	$42.46	$42.45	$42.50
Purchase #5	$102.93	12.814%	$116.1195	$116.12	$116.10	$116.10
Purchase #6	$6.72	10.589%	$7.4316	$7.43	$7.45	$7.40
Purchase #7	$196.38	3.490%	$203.2337	$203.23	$203.25	$203.20
7 purchase totals =	$757.69		$812.6776	$812.67	$812.70	$812.60