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	$152.30	4.815%	$159.6332	$159.63	$159.65	$159.60
Purchase #2	$121.31	5.645%	$128.1579	$128.16	$128.15	$128.20
Purchase #3	$13.43	10.874%	$14.8904	$14.89	$14.90	$14.90
Purchase #4	$237.37	9.339%	$259.538	$259.54	$259.55	$259.50
Purchase #5	$78.58	12.302%	$88.2469	$88.25	$88.25	$88.20
Purchase #6	$220.55	4.662%	$230.832	$230.83	$230.85	$230.80
Purchase #7	$147.44	12.142%	$165.3422	$165.34	$165.35	$165.30
7 purchase totals =	$970.98		$1,046.6406	$1,046.64	$1,046.70	$1,046.50