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	$172.29	7.120%	$184.557	$184.56	$184.55	$184.60
Purchase #2	$147.72	6.645%	$157.536	$157.54	$157.55	$157.50
Purchase #3	$85.74	4.369%	$89.486	$89.49	$89.50	$89.50
Purchase #4	$153.53	8.524%	$166.6169	$166.62	$166.60	$166.60
Purchase #5	$124.75	13.339%	$141.3904	$141.39	$141.40	$141.40
Purchase #6	$167.73	13.555%	$190.4658	$190.47	$190.45	$190.50
Purchase #7	$189.74	3.709%	$196.7775	$196.78	$196.80	$196.80
7 purchase totals =	$1,041.50		$1,126.8296	$1,126.85	$1,126.85	$1,126.90