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	$174.97	13.218%	$198.0975	$198.10	$198.10	$198.10
Purchase #2	$84.87	6.203%	$90.1345	$90.13	$90.15	$90.10
Purchase #3	$155.55	6.567%	$165.765	$165.77	$165.75	$165.80
Purchase #4	$201.53	7.108%	$215.8548	$215.85	$215.85	$215.90
Purchase #5	$229.59	11.520%	$256.0388	$256.04	$256.05	$256.00
Purchase #6	$17.52	8.287%	$18.9719	$18.97	$18.95	$19.00
Purchase #7	$32.34	4.183%	$33.6928	$33.69	$33.70	$33.70
7 purchase totals =	$896.37		$978.5553	$978.55	$978.55	$978.60