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	$226.71	12.277%	$254.5432	$254.54	$254.55	$254.50
Purchase #2	$50.89	5.204%	$53.5383	$53.54	$53.55	$53.50
Purchase #3	$18.52	11.842%	$20.7131	$20.71	$20.70	$20.70
Purchase #4	$150.90	12.384%	$169.5875	$169.59	$169.60	$169.60
Purchase #5	$146.62	13.705%	$166.7143	$166.71	$166.70	$166.70
Purchase #6	$249.94	11.620%	$278.983	$278.98	$279.00	$279.00
Purchase #7	$238.99	12.716%	$269.38	$269.38	$269.40	$269.40
7 purchase totals =	$1,082.57		$1,213.4594	$1,213.45	$1,213.50	$1,213.40