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	$56.85	4.501%	$59.4088	$59.41	$59.40	$59.40
Purchase #2	$220.61	9.343%	$241.2216	$241.22	$241.20	$241.20
Purchase #3	$170.64	11.215%	$189.7773	$189.78	$189.80	$189.80
Purchase #4	$163.50	4.541%	$170.9245	$170.92	$170.90	$170.90
Purchase #5	$168.92	5.496%	$178.2038	$178.20	$178.20	$178.20
Purchase #6	$170.43	8.865%	$185.5386	$185.54	$185.55	$185.50
Purchase #7	$88.30	12.520%	$99.3552	$99.36	$99.35	$99.40
7 purchase totals =	$1,039.25		$1,124.4298	$1,124.43	$1,124.40	$1,124.40