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	$195.51	11.397%	$217.7923	$217.79	$217.80	$217.80
Purchase #2	$58.32	13.352%	$66.1069	$66.11	$66.10	$66.10
Purchase #3	$104.86	13.122%	$118.6197	$118.62	$118.60	$118.60
Purchase #4	$54.54	4.707%	$57.1072	$57.11	$57.10	$57.10
Purchase #5	$71.28	3.280%	$73.618	$73.62	$73.60	$73.60
Purchase #6	$53.61	10.728%	$59.3613	$59.36	$59.35	$59.40
Purchase #7	$221.89	7.626%	$238.8113	$238.81	$238.80	$238.80
7 purchase totals =	$760.01		$831.4167	$831.42	$831.35	$831.40