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	$130.35	11.387%	$145.193	$145.19	$145.20	$145.20
Purchase #2	$178.72	3.292%	$184.6035	$184.60	$184.60	$184.60
Purchase #3	$30.35	3.131%	$31.3003	$31.30	$31.30	$31.30
Purchase #4	$119.61	9.270%	$130.6978	$130.70	$130.70	$130.70
Purchase #5	$105.30	11.778%	$117.7022	$117.70	$117.70	$117.70
Purchase #6	$200.34	11.579%	$223.5374	$223.54	$223.55	$223.50
Purchase #7	$54.63	8.142%	$59.078	$59.08	$59.10	$59.10
7 purchase totals =	$819.30		$892.1122	$892.11	$892.15	$892.10