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	$125.69	13.406%	$142.54	$142.54	$142.55	$142.50
Purchase #2	$164.58	5.488%	$173.6122	$173.61	$173.60	$173.60
Purchase #3	$229.64	11.543%	$256.1473	$256.15	$256.15	$256.10
Purchase #4	$170.34	11.646%	$190.1778	$190.18	$190.20	$190.20
Purchase #5	$212.95	13.118%	$240.8848	$240.88	$240.90	$240.90
Purchase #6	$182.47	4.850%	$191.3198	$191.32	$191.30	$191.30
Purchase #7	$155.30	11.318%	$172.8769	$172.88	$172.90	$172.90
7 purchase totals =	$1,240.97		$1,367.5588	$1,367.56	$1,367.60	$1,367.50