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	$214.67	6.688%	$229.0271	$229.03	$229.05	$229.00
Purchase #2	$243.69	3.638%	$252.5554	$252.56	$252.55	$252.60
Purchase #3	$27.31	3.510%	$28.2686	$28.27	$28.25	$28.30
Purchase #4	$49.86	11.496%	$55.5919	$55.59	$55.60	$55.60
Purchase #5	$88.32	13.773%	$100.4843	$100.48	$100.50	$100.50
Purchase #6	$202.51	6.287%	$215.2418	$215.24	$215.25	$215.20
Purchase #7	$53.82	3.512%	$55.7102	$55.71	$55.70	$55.70
7 purchase totals =	$880.18		$936.8793	$936.88	$936.90	$936.90