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	$45.57	10.456%	$50.3348	$50.33	$50.35	$50.30
Purchase #2	$230.45	11.298%	$256.4862	$256.49	$256.50	$256.50
Purchase #3	$93.67	6.486%	$99.7454	$99.75	$99.75	$99.70
Purchase #4	$120.59	4.310%	$125.7874	$125.79	$125.80	$125.80
Purchase #5	$174.63	10.197%	$192.437	$192.44	$192.45	$192.40
Purchase #6	$31.84	10.844%	$35.2927	$35.29	$35.30	$35.30
Purchase #7	$250.72	13.454%	$284.4519	$284.45	$284.45	$284.50
7 purchase totals =	$947.47		$1,044.5354	$1,044.54	$1,044.60	$1,044.50