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	$200.75	13.542%	$227.9356	$227.94	$227.95	$227.90
Purchase #2	$199.40	6.736%	$212.8316	$212.83	$212.85	$212.80
Purchase #3	$65.31	11.619%	$72.8984	$72.90	$72.90	$72.90
Purchase #4	$41.67	10.734%	$46.1429	$46.14	$46.15	$46.10
Purchase #5	$209.53	11.797%	$234.2483	$234.25	$234.25	$234.20
Purchase #6	$32.45	4.162%	$33.8006	$33.80	$33.80	$33.80
Purchase #7	$88.38	7.124%	$94.6762	$94.68	$94.70	$94.70
7 purchase totals =	$837.49		$922.5336	$922.54	$922.60	$922.40