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	$51.45	12.285%	$57.7706	$57.77	$57.75	$57.80
Purchase #2	$223.41	8.206%	$241.743	$241.74	$241.75	$241.70
Purchase #3	$195.42	9.116%	$213.2345	$213.23	$213.25	$213.20
Purchase #4	$40.89	11.501%	$45.5928	$45.59	$45.60	$45.60
Purchase #5	$75.38	9.206%	$82.3195	$82.32	$82.30	$82.30
Purchase #6	$11.83	5.625%	$12.4954	$12.50	$12.50	$12.50
Purchase #7	$99.36	6.764%	$106.0807	$106.08	$106.10	$106.10
7 purchase totals =	$697.74		$759.2365	$759.23	$759.25	$759.20