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	$56.84	7.619%	$61.1706	$61.17	$61.15	$61.20
Purchase #2	$61.89	8.695%	$67.2713	$67.27	$67.25	$67.30
Purchase #3	$23.29	4.531%	$24.3453	$24.35	$24.35	$24.30
Purchase #4	$31.55	8.710%	$34.298	$34.30	$34.30	$34.30
Purchase #5	$158.31	4.546%	$165.5068	$165.51	$165.50	$165.50
Purchase #6	$198.27	4.146%	$206.4903	$206.49	$206.50	$206.50
Purchase #7	$223.83	11.805%	$250.2531	$250.25	$250.25	$250.30
7 purchase totals =	$753.98		$809.3354	$809.34	$809.30	$809.40