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	$173.49	10.108%	$191.0264	$191.03	$191.05	$191.00
Purchase #2	$59.48	9.529%	$65.1478	$65.15	$65.15	$65.10
Purchase #3	$148.57	7.337%	$159.4706	$159.47	$159.45	$159.50
Purchase #4	$72.65	3.549%	$75.2283	$75.23	$75.25	$75.20
Purchase #5	$38.29	5.219%	$40.2884	$40.29	$40.30	$40.30
Purchase #6	$182.45	5.166%	$191.8754	$191.88	$191.90	$191.90
Purchase #7	$41.67	8.443%	$45.1882	$45.19	$45.20	$45.20
7 purchase totals =	$716.60		$768.2251	$768.24	$768.30	$768.20