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	$82.89	11.307%	$92.2624	$92.26	$92.25	$92.30
Purchase #2	$123.68	10.671%	$136.8779	$136.88	$136.90	$136.90
Purchase #3	$91.72	3.767%	$95.1751	$95.18	$95.20	$95.20
Purchase #4	$245.62	7.842%	$264.8815	$264.88	$264.90	$264.90
Purchase #5	$32.30	4.312%	$33.6928	$33.69	$33.70	$33.70
Purchase #6	$187.55	13.506%	$212.8805	$212.88	$212.90	$212.90
Purchase #7	$91.88	7.297%	$98.5845	$98.58	$98.60	$98.60
7 purchase totals =	$855.64		$934.3547	$934.35	$934.45	$934.50