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	$80.60	3.560%	$83.4694	$83.47	$83.45	$83.50
Purchase #2	$157.52	7.685%	$169.6254	$169.63	$169.65	$169.60
Purchase #3	$182.71	5.231%	$192.2676	$192.27	$192.25	$192.30
Purchase #4	$61.61	9.639%	$67.5486	$67.55	$67.55	$67.50
Purchase #5	$61.96	9.749%	$68.0005	$68.00	$68.00	$68.00
Purchase #6	$54.79	8.872%	$59.651	$59.65	$59.65	$59.70
Purchase #7	$108.89	4.594%	$113.8924	$113.89	$113.90	$113.90
7 purchase totals =	$708.08		$754.4549	$754.46	$754.45	$754.50