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	$115.56	8.667%	$125.5756	$125.58	$125.60	$125.60
Purchase #2	$50.57	5.445%	$53.3235	$53.32	$53.30	$53.30
Purchase #3	$12.51	7.767%	$13.4817	$13.48	$13.50	$13.50
Purchase #4	$15.84	13.108%	$17.9163	$17.92	$17.90	$17.90
Purchase #5	$177.53	12.731%	$200.1313	$200.13	$200.15	$200.10
Purchase #6	$99.72	3.673%	$103.3827	$103.38	$103.40	$103.40
Purchase #7	$172.73	7.626%	$185.9024	$185.90	$185.90	$185.90
7 purchase totals =	$644.46		$699.7135	$699.71	$699.75	$699.70