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	$88.48	3.160%	$91.276	$91.28	$91.30	$91.30
Purchase #2	$10.69	7.459%	$11.4874	$11.49	$11.50	$11.50
Purchase #3	$231.55	3.170%	$238.8901	$238.89	$238.90	$238.90
Purchase #4	$100.65	3.111%	$103.7812	$103.78	$103.80	$103.80
Purchase #5	$120.31	10.571%	$133.028	$133.03	$133.05	$133.00
Purchase #6	$81.34	10.618%	$89.9767	$89.98	$90.00	$90.00
Purchase #7	$26.60	11.724%	$29.7186	$29.72	$29.70	$29.70
7 purchase totals =	$659.62		$698.1580	$698.17	$698.25	$698.20