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	$222.66	10.283%	$245.5561	$245.56	$245.55	$245.60
Purchase #2	$215.76	11.163%	$239.8453	$239.85	$239.85	$239.80
Purchase #3	$112.89	13.863%	$128.5399	$128.54	$128.55	$128.50
Purchase #4	$231.96	13.639%	$263.597	$263.60	$263.60	$263.60
Purchase #5	$25.31	10.190%	$27.8891	$27.89	$27.90	$27.90
Purchase #6	$7.47	9.512%	$8.1805	$8.18	$8.20	$8.20
Purchase #7	$93.55	10.275%	$103.1623	$103.16	$103.15	$103.20
7 purchase totals =	$909.60		$1,016.7702	$1,016.78	$1,016.80	$1,016.80