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	$64.79	11.223%	$72.0614	$72.06	$72.05	$72.10
Purchase #2	$121.65	4.843%	$127.5415	$127.54	$127.55	$127.50
Purchase #3	$85.65	5.290%	$90.1809	$90.18	$90.20	$90.20
Purchase #4	$6.74	10.870%	$7.4726	$7.47	$7.45	$7.50
Purchase #5	$139.63	7.594%	$150.2335	$150.23	$150.25	$150.20
Purchase #6	$111.82	10.662%	$123.7422	$123.74	$123.75	$123.70
Purchase #7	$99.59	12.676%	$112.214	$112.21	$112.20	$112.20
7 purchase totals =	$629.87		$683.4461	$683.43	$683.45	$683.40