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	$65.97	10.534%	$72.9193	$72.92	$72.90	$72.90
Purchase #2	$136.46	11.552%	$152.2239	$152.22	$152.20	$152.20
Purchase #3	$121.94	12.766%	$137.5069	$137.51	$137.50	$137.50
Purchase #4	$154.80	11.584%	$172.732	$172.73	$172.75	$172.70
Purchase #5	$24.87	9.835%	$27.316	$27.32	$27.30	$27.30
Purchase #6	$208.72	11.845%	$233.4429	$233.44	$233.45	$233.40
Purchase #7	$136.65	10.797%	$151.4041	$151.40	$151.40	$151.40
7 purchase totals =	$849.41		$947.5451	$947.54	$947.50	$947.40