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	$205.50	8.487%	$222.9408	$222.94	$222.95	$222.90
Purchase #2	$97.48	6.266%	$103.5881	$103.59	$103.60	$103.60
Purchase #3	$184.85	4.690%	$193.5195	$193.52	$193.50	$193.50
Purchase #4	$37.50	11.465%	$41.7994	$41.80	$41.80	$41.80
Purchase #5	$73.53	8.423%	$79.7234	$79.72	$79.70	$79.70
Purchase #6	$83.76	6.114%	$88.8811	$88.88	$88.90	$88.90
Purchase #7	$34.70	3.234%	$35.8222	$35.82	$35.80	$35.80
7 purchase totals =	$717.32		$766.2745	$766.27	$766.25	$766.20