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	$244.48	7.801%	$263.5519	$263.55	$263.55	$263.60
Purchase #2	$131.48	8.266%	$142.3481	$142.35	$142.35	$142.30
Purchase #3	$248.33	3.210%	$256.3014	$256.30	$256.30	$256.30
Purchase #4	$214.95	8.405%	$233.0165	$233.02	$233.00	$233.00
Purchase #5	$167.54	10.634%	$185.3562	$185.36	$185.35	$185.40
Purchase #6	$143.69	11.496%	$160.2086	$160.21	$160.20	$160.20
Purchase #7	$162.77	6.359%	$173.1205	$173.12	$173.10	$173.10
7 purchase totals =	$1,313.24		$1,413.9032	$1,413.91	$1,413.85	$1,413.90