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	$43.89	6.817%	$46.882	$46.88	$46.90	$46.90
Purchase #2	$17.61	13.857%	$20.0502	$20.05	$20.05	$20.10
Purchase #3	$43.56	3.471%	$45.072	$45.07	$45.05	$45.10
Purchase #4	$156.72	7.726%	$168.8282	$168.83	$168.85	$168.80
Purchase #5	$36.78	10.221%	$40.5393	$40.54	$40.55	$40.50
Purchase #6	$44.70	7.590%	$48.0927	$48.09	$48.10	$48.10
Purchase #7	$84.88	7.474%	$91.2239	$91.22	$91.20	$91.20
7 purchase totals =	$428.14		$460.6883	$460.68	$460.70	$460.70