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	$32.41	9.208%	$35.3943	$35.39	$35.40	$35.40
Purchase #2	$180.46	11.212%	$200.6932	$200.69	$200.70	$200.70
Purchase #3	$235.54	10.759%	$260.8817	$260.88	$260.90	$260.90
Purchase #4	$90.89	7.872%	$98.0449	$98.04	$98.05	$98.00
Purchase #5	$28.88	6.253%	$30.6859	$30.69	$30.70	$30.70
Purchase #6	$88.55	3.729%	$91.852	$91.85	$91.85	$91.90
Purchase #7	$9.88	10.576%	$10.9249	$10.92	$10.90	$10.90
7 purchase totals =	$666.61		$728.4769	$728.46	$728.50	$728.50