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	$111.61	5.855%	$118.1448	$118.14	$118.15	$118.10
Purchase #2	$104.25	13.861%	$118.7001	$118.70	$118.70	$118.70
Purchase #3	$59.56	10.624%	$65.8877	$65.89	$65.90	$65.90
Purchase #4	$105.49	3.442%	$109.121	$109.12	$109.10	$109.10
Purchase #5	$83.54	3.338%	$86.3286	$86.33	$86.35	$86.30
Purchase #6	$42.89	8.309%	$46.4537	$46.45	$46.45	$46.50
Purchase #7	$172.50	5.334%	$181.7012	$181.70	$181.70	$181.70
7 purchase totals =	$679.84		$726.3371	$726.33	$726.35	$726.30