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	$112.55	10.403%	$124.2586	$124.26	$124.25	$124.30
Purchase #2	$39.32	11.292%	$43.76	$43.76	$43.75	$43.80
Purchase #3	$232.50	12.813%	$262.2902	$262.29	$262.30	$262.30
Purchase #4	$185.77	13.487%	$210.8248	$210.82	$210.80	$210.80
Purchase #5	$227.34	3.303%	$234.849	$234.85	$234.85	$234.80
Purchase #6	$31.94	11.223%	$35.5246	$35.52	$35.50	$35.50
Purchase #7	$126.34	13.814%	$143.7926	$143.79	$143.80	$143.80
7 purchase totals =	$955.76		$1,055.2998	$1,055.29	$1,055.25	$1,055.30