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	$206.69	13.646%	$234.8949	$234.89	$234.90	$234.90
Purchase #2	$68.69	10.110%	$75.6346	$75.63	$75.65	$75.60
Purchase #3	$139.59	9.726%	$153.1665	$153.17	$153.15	$153.20
Purchase #4	$211.82	10.523%	$234.1098	$234.11	$234.10	$234.10
Purchase #5	$90.43	8.822%	$98.4077	$98.41	$98.40	$98.40
Purchase #6	$111.53	10.401%	$123.1302	$123.13	$123.15	$123.10
Purchase #7	$212.31	10.155%	$233.8701	$233.87	$233.85	$233.90
7 purchase totals =	$1,041.06		$1,153.2138	$1,153.21	$1,153.20	$1,153.20