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	$31.61	5.814%	$33.4478	$33.45	$33.45	$33.40
Purchase #2	$174.88	10.111%	$192.5621	$192.56	$192.55	$192.60
Purchase #3	$163.66	8.384%	$177.3813	$177.38	$177.40	$177.40
Purchase #4	$237.57	10.460%	$262.4198	$262.42	$262.40	$262.40
Purchase #5	$99.28	10.585%	$109.7888	$109.79	$109.80	$109.80
Purchase #6	$53.74	11.363%	$59.8465	$59.85	$59.85	$59.80
Purchase #7	$130.73	4.492%	$136.6024	$136.60	$136.60	$136.60
7 purchase totals =	$891.47		$972.0487	$972.05	$972.05	$972.00