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	$58.34	9.514%	$63.8905	$63.89	$63.90	$63.90
Purchase #2	$191.51	13.743%	$217.8292	$217.83	$217.85	$217.80
Purchase #3	$178.40	4.173%	$185.8446	$185.84	$185.85	$185.80
Purchase #4	$35.36	6.767%	$37.7528	$37.75	$37.75	$37.80
Purchase #5	$75.66	8.750%	$82.2803	$82.28	$82.30	$82.30
Purchase #6	$77.25	6.179%	$82.0233	$82.02	$82.00	$82.00
Purchase #7	$56.79	9.129%	$61.9744	$61.97	$61.95	$62.00
7 purchase totals =	$673.31		$731.5951	$731.58	$731.60	$731.60