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	$101.25	3.756%	$105.053	$105.05	$105.05	$105.10
Purchase #2	$103.85	9.284%	$113.4914	$113.49	$113.50	$113.50
Purchase #3	$36.55	9.588%	$40.0544	$40.05	$40.05	$40.10
Purchase #4	$43.78	6.159%	$46.4764	$46.48	$46.50	$46.50
Purchase #5	$237.85	10.618%	$263.1049	$263.10	$263.10	$263.10
Purchase #6	$140.97	7.104%	$150.9845	$150.98	$151.00	$151.00
Purchase #7	$18.85	7.506%	$20.2649	$20.26	$20.25	$20.30
7 purchase totals =	$683.10		$739.4295	$739.41	$739.45	$739.60