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	$127.59	12.539%	$143.5885	$143.59	$143.60	$143.60
Purchase #2	$39.76	8.506%	$43.142	$43.14	$43.15	$43.10
Purchase #3	$19.54	11.184%	$21.7254	$21.73	$21.75	$21.70
Purchase #4	$200.63	4.607%	$209.873	$209.87	$209.85	$209.90
Purchase #5	$95.62	11.787%	$106.8907	$106.89	$106.90	$106.90
Purchase #6	$211.35	10.554%	$233.6559	$233.66	$233.65	$233.70
Purchase #7	$248.71	5.346%	$262.006	$262.01	$262.00	$262.00
7 purchase totals =	$943.20		$1,020.8815	$1,020.89	$1,020.90	$1,020.90