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	$102.63	7.321%	$110.1435	$110.14	$110.15	$110.10
Purchase #2	$76.61	3.319%	$79.1527	$79.15	$79.15	$79.20
Purchase #3	$104.69	9.570%	$114.7088	$114.71	$114.70	$114.70
Purchase #4	$54.97	7.723%	$59.2153	$59.22	$59.20	$59.20
Purchase #5	$230.72	5.377%	$243.1258	$243.13	$243.15	$243.10
Purchase #6	$25.47	10.490%	$28.1418	$28.14	$28.15	$28.10
Purchase #7	$67.82	4.480%	$70.8583	$70.86	$70.85	$70.90
7 purchase totals =	$662.91		$705.3462	$705.35	$705.35	$705.30