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	$93.89	11.369%	$104.5644	$104.56	$104.55	$104.60
Purchase #2	$133.35	6.198%	$141.615	$141.62	$141.60	$141.60
Purchase #3	$130.60	7.509%	$140.4068	$140.41	$140.40	$140.40
Purchase #4	$9.71	4.234%	$10.1211	$10.12	$10.10	$10.10
Purchase #5	$82.31	4.557%	$86.0609	$86.06	$86.05	$86.10
Purchase #6	$187.28	4.732%	$196.1421	$196.14	$196.15	$196.10
Purchase #7	$22.74	8.122%	$24.5869	$24.59	$24.60	$24.60
7 purchase totals =	$659.88		$703.4972	$703.50	$703.45	$703.50