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	$53.33	4.215%	$55.5779	$55.58	$55.60	$55.60
Purchase #2	$149.92	8.650%	$162.8881	$162.89	$162.90	$162.90
Purchase #3	$140.39	8.749%	$152.6727	$152.67	$152.65	$152.70
Purchase #4	$22.94	6.187%	$24.3593	$24.36	$24.35	$24.40
Purchase #5	$144.79	13.777%	$164.7377	$164.74	$164.75	$164.70
Purchase #6	$39.76	5.254%	$41.849	$41.85	$41.85	$41.80
Purchase #7	$148.96	10.457%	$164.5367	$164.54	$164.55	$164.50
7 purchase totals =	$700.09		$766.6214	$766.63	$766.65	$766.60