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	$190.66	13.109%	$215.6536	$215.65	$215.65	$215.70
Purchase #2	$242.70	5.774%	$256.7135	$256.71	$256.70	$256.70
Purchase #3	$136.34	10.132%	$150.154	$150.15	$150.15	$150.20
Purchase #4	$73.58	9.195%	$80.3457	$80.35	$80.35	$80.30
Purchase #5	$65.63	8.489%	$71.2013	$71.20	$71.20	$71.20
Purchase #6	$99.79	4.106%	$103.8874	$103.89	$103.90	$103.90
Purchase #7	$143.36	10.657%	$158.6379	$158.64	$158.65	$158.60
7 purchase totals =	$952.06		$1,036.5934	$1,036.59	$1,036.60	$1,036.60