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	$10.41	9.754%	$11.4254	$11.43	$11.45	$11.40
Purchase #2	$43.86	6.586%	$46.7486	$46.75	$46.75	$46.70
Purchase #3	$44.69	7.555%	$48.0663	$48.07	$48.05	$48.10
Purchase #4	$89.86	7.591%	$96.6813	$96.68	$96.70	$96.70
Purchase #5	$9.38	11.584%	$10.4666	$10.47	$10.45	$10.50
Purchase #6	$110.69	11.797%	$123.7481	$123.75	$123.75	$123.70
Purchase #7	$79.78	7.155%	$85.4883	$85.49	$85.50	$85.50
7 purchase totals =	$388.67		$422.6246	$422.64	$422.65	$422.60