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	$135.30	4.832%	$141.8377	$141.84	$141.85	$141.80
Purchase #2	$125.91	6.363%	$133.9217	$133.92	$133.90	$133.90
Purchase #3	$122.53	6.519%	$130.5177	$130.52	$130.50	$130.50
Purchase #4	$43.31	11.600%	$48.334	$48.33	$48.35	$48.30
Purchase #5	$196.80	13.607%	$223.5786	$223.58	$223.60	$223.60
Purchase #6	$244.48	4.114%	$254.5379	$254.54	$254.55	$254.50
Purchase #7	$87.83	3.774%	$91.1447	$91.14	$91.15	$91.10
7 purchase totals =	$956.16		$1,023.8723	$1,023.87	$1,023.90	$1,023.70