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	$161.72	13.813%	$184.0584	$184.06	$184.05	$184.10
Purchase #2	$19.57	8.539%	$21.2411	$21.24	$21.25	$21.20
Purchase #3	$138.62	7.385%	$148.8571	$148.86	$148.85	$148.90
Purchase #4	$23.87	3.365%	$24.6732	$24.67	$24.65	$24.70
Purchase #5	$147.83	11.543%	$164.894	$164.89	$164.90	$164.90
Purchase #6	$67.34	6.741%	$71.8794	$71.88	$71.90	$71.90
Purchase #7	$119.55	5.685%	$126.3464	$126.35	$126.35	$126.30
7 purchase totals =	$678.50		$741.9496	$741.95	$741.95	$742.00