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	$125.52	9.565%	$137.526	$137.53	$137.55	$137.50
Purchase #2	$34.90	8.414%	$37.8365	$37.84	$37.85	$37.80
Purchase #3	$137.91	11.752%	$154.1172	$154.12	$154.10	$154.10
Purchase #4	$20.84	5.856%	$22.0604	$22.06	$22.05	$22.10
Purchase #5	$50.86	6.462%	$54.1466	$54.15	$54.15	$54.10
Purchase #6	$87.89	13.378%	$99.6479	$99.65	$99.65	$99.60
Purchase #7	$212.88	13.353%	$241.3059	$241.31	$241.30	$241.30
7 purchase totals =	$670.80		$746.6405	$746.66	$746.65	$746.50