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	$189.91	13.273%	$215.1168	$215.12	$215.10	$215.10
Purchase #2	$150.73	11.581%	$168.186	$168.19	$168.20	$168.20
Purchase #3	$148.86	4.746%	$155.9249	$155.92	$155.90	$155.90
Purchase #4	$165.99	3.674%	$172.0885	$172.09	$172.10	$172.10
Purchase #5	$47.84	9.580%	$52.4231	$52.42	$52.40	$52.40
Purchase #6	$33.27	10.377%	$36.7224	$36.72	$36.70	$36.70
Purchase #7	$243.78	5.231%	$256.5321	$256.53	$256.55	$256.50
7 purchase totals =	$980.38		$1,056.9938	$1,056.99	$1,056.95	$1,056.90