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	$161.78	11.678%	$180.6727	$180.67	$180.65	$180.70
Purchase #2	$124.63	9.564%	$136.5496	$136.55	$136.55	$136.50
Purchase #3	$79.63	7.103%	$85.2861	$85.29	$85.30	$85.30
Purchase #4	$48.47	10.508%	$53.5632	$53.56	$53.55	$53.60
Purchase #5	$242.30	7.248%	$259.8619	$259.86	$259.85	$259.90
Purchase #6	$102.83	3.399%	$106.3252	$106.33	$106.35	$106.30
Purchase #7	$47.54	12.191%	$53.3356	$53.34	$53.35	$53.30
7 purchase totals =	$807.18		$875.5943	$875.60	$875.60	$875.60