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	$43.83	4.354%	$45.7384	$45.74	$45.75	$45.70
Purchase #2	$172.89	13.587%	$196.3806	$196.38	$196.40	$196.40
Purchase #3	$42.65	8.449%	$46.2535	$46.25	$46.25	$46.30
Purchase #4	$46.77	6.560%	$49.8381	$49.84	$49.85	$49.80
Purchase #5	$20.29	12.323%	$22.7903	$22.79	$22.80	$22.80
Purchase #6	$78.52	6.625%	$83.722	$83.72	$83.70	$83.70
Purchase #7	$164.89	6.402%	$175.4463	$175.45	$175.45	$175.40
7 purchase totals =	$569.84		$620.1692	$620.17	$620.20	$620.10