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	$62.62	7.556%	$67.3516	$67.35	$67.35	$67.40
Purchase #2	$31.56	3.328%	$32.6103	$32.61	$32.60	$32.60
Purchase #3	$71.45	8.141%	$77.2667	$77.27	$77.25	$77.30
Purchase #4	$245.56	11.288%	$273.2788	$273.28	$273.30	$273.30
Purchase #5	$221.89	13.276%	$251.3481	$251.35	$251.35	$251.30
Purchase #6	$92.26	7.574%	$99.2478	$99.25	$99.25	$99.20
Purchase #7	$165.90	8.560%	$180.101	$180.10	$180.10	$180.10
7 purchase totals =	$891.24		$981.2043	$981.21	$981.20	$981.20