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	$248.63	4.154%	$258.9581	$258.96	$258.95	$259.00
Purchase #2	$148.55	5.111%	$156.1424	$156.14	$156.15	$156.10
Purchase #3	$243.42	5.408%	$256.5842	$256.58	$256.60	$256.60
Purchase #4	$144.25	3.532%	$149.3449	$149.34	$149.35	$149.30
Purchase #5	$122.59	12.316%	$137.6882	$137.69	$137.70	$137.70
Purchase #6	$104.49	6.772%	$111.5661	$111.57	$111.55	$111.60
Purchase #7	$109.33	13.815%	$124.4339	$124.43	$124.45	$124.40
7 purchase totals =	$1,121.26		$1,194.7178	$1,194.71	$1,194.75	$1,194.70