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	$35.61	4.645%	$37.2641	$37.26	$37.25	$37.30
Purchase #2	$180.67	5.871%	$191.2771	$191.28	$191.30	$191.30
Purchase #3	$51.43	9.392%	$56.2603	$56.26	$56.25	$56.30
Purchase #4	$68.33	6.102%	$72.4995	$72.50	$72.50	$72.50
Purchase #5	$244.60	9.468%	$267.7587	$267.76	$267.75	$267.80
Purchase #6	$153.87	7.210%	$164.964	$164.96	$164.95	$165.00
Purchase #7	$95.84	6.588%	$102.1539	$102.15	$102.15	$102.20
7 purchase totals =	$830.35		$892.1776	$892.17	$892.15	$892.40