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	$151.32	3.510%	$156.6313	$156.63	$156.65	$156.60
Purchase #2	$57.70	3.254%	$59.5776	$59.58	$59.60	$59.60
Purchase #3	$70.68	12.625%	$79.6034	$79.60	$79.60	$79.60
Purchase #4	$73.78	6.825%	$78.8155	$78.82	$78.80	$78.80
Purchase #5	$187.56	6.334%	$199.4401	$199.44	$199.45	$199.40
Purchase #6	$141.31	5.198%	$148.6553	$148.66	$148.65	$148.70
Purchase #7	$229.67	13.589%	$260.8799	$260.88	$260.90	$260.90
7 purchase totals =	$912.02		$983.6031	$983.61	$983.65	$983.60