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	$53.67	6.492%	$57.1543	$57.15	$57.15	$57.20
Purchase #2	$10.43	6.536%	$11.1117	$11.11	$11.10	$11.10
Purchase #3	$48.87	6.402%	$51.9987	$52.00	$52.00	$52.00
Purchase #4	$136.75	13.619%	$155.374	$155.37	$155.35	$155.40
Purchase #5	$52.53	13.173%	$59.4498	$59.45	$59.45	$59.40
Purchase #6	$216.26	3.205%	$223.1911	$223.19	$223.20	$223.20
Purchase #7	$99.49	5.557%	$105.0187	$105.02	$105.00	$105.00
7 purchase totals =	$618.00		$663.2983	$663.29	$663.25	$663.30