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	$48.82	11.679%	$54.5217	$54.52	$54.50	$54.50
Purchase #2	$44.95	8.367%	$48.711	$48.71	$48.70	$48.70
Purchase #3	$91.52	4.523%	$95.6594	$95.66	$95.65	$95.70
Purchase #4	$31.55	11.683%	$35.236	$35.24	$35.25	$35.20
Purchase #5	$89.84	7.804%	$96.8511	$96.85	$96.85	$96.90
Purchase #6	$151.46	11.461%	$168.8188	$168.82	$168.80	$168.80
Purchase #7	$203.78	12.438%	$229.1262	$229.13	$229.15	$229.10
7 purchase totals =	$661.92		$728.9242	$728.93	$728.90	$728.90