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	$102.54	6.386%	$109.0882	$109.09	$109.10	$109.10
Purchase #2	$217.62	5.525%	$229.6435	$229.64	$229.65	$229.60
Purchase #3	$145.52	13.853%	$165.6789	$165.68	$165.70	$165.70
Purchase #4	$226.69	7.132%	$242.8575	$242.86	$242.85	$242.90
Purchase #5	$87.35	13.401%	$99.0558	$99.06	$99.05	$99.10
Purchase #6	$83.69	12.140%	$93.85	$93.85	$93.85	$93.90
Purchase #7	$149.92	7.239%	$160.7727	$160.77	$160.75	$160.80
7 purchase totals =	$1,013.33		$1,100.9466	$1,100.95	$1,100.95	$1,101.10