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	$57.30	3.830%	$59.4946	$59.49	$59.50	$59.50
Purchase #2	$209.46	10.822%	$232.1278	$232.13	$232.15	$232.10
Purchase #3	$105.25	12.714%	$118.6315	$118.63	$118.65	$118.60
Purchase #4	$50.26	4.288%	$52.4151	$52.42	$52.40	$52.40
Purchase #5	$55.94	6.305%	$59.467	$59.47	$59.45	$59.50
Purchase #6	$53.49	13.454%	$60.6865	$60.69	$60.70	$60.70
Purchase #7	$68.75	5.208%	$72.3305	$72.33	$72.35	$72.30
7 purchase totals =	$600.45		$655.1530	$655.16	$655.20	$655.10