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	$225.80	7.125%	$241.8883	$241.89	$241.90	$241.90
Purchase #2	$181.56	8.466%	$196.9309	$196.93	$196.95	$196.90
Purchase #3	$178.53	7.364%	$191.6769	$191.68	$191.70	$191.70
Purchase #4	$8.58	3.477%	$8.8783	$8.88	$8.90	$8.90
Purchase #5	$79.41	11.579%	$88.6049	$88.60	$88.60	$88.60
Purchase #6	$208.94	9.431%	$228.6451	$228.65	$228.65	$228.60
Purchase #7	$80.32	11.725%	$89.7375	$89.74	$89.75	$89.70
7 purchase totals =	$963.14		$1,046.3619	$1,046.37	$1,046.45	$1,046.30