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	$112.72	9.628%	$123.5727	$123.57	$123.55	$123.60
Purchase #2	$147.58	8.197%	$159.6771	$159.68	$159.70	$159.70
Purchase #3	$19.43	13.708%	$22.0935	$22.09	$22.10	$22.10
Purchase #4	$40.34	4.705%	$42.238	$42.24	$42.25	$42.20
Purchase #5	$45.63	3.699%	$47.3179	$47.32	$47.30	$47.30
Purchase #6	$93.93	11.454%	$104.6887	$104.69	$104.70	$104.70
Purchase #7	$87.68	3.386%	$90.6488	$90.65	$90.65	$90.60
7 purchase totals =	$547.31		$590.2367	$590.24	$590.25	$590.20