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	$163.50	13.369%	$185.3583	$185.36	$185.35	$185.40
Purchase #2	$216.99	3.641%	$224.8906	$224.89	$224.90	$224.90
Purchase #3	$103.57	5.386%	$109.1483	$109.15	$109.15	$109.10
Purchase #4	$104.72	6.525%	$111.553	$111.55	$111.55	$111.60
Purchase #5	$37.94	6.276%	$40.3211	$40.32	$40.30	$40.30
Purchase #6	$90.54	11.313%	$100.7828	$100.78	$100.80	$100.80
Purchase #7	$245.77	7.414%	$263.9914	$263.99	$264.00	$264.00
7 purchase totals =	$963.03		$1,036.0455	$1,036.04	$1,036.05	$1,036.10