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	$35.65	5.654%	$37.6657	$37.67	$37.65	$37.70
Purchase #2	$59.60	3.633%	$61.7653	$61.77	$61.75	$61.80
Purchase #3	$141.37	7.491%	$151.96	$151.96	$151.95	$152.00
Purchase #4	$146.40	3.522%	$151.5562	$151.56	$151.55	$151.60
Purchase #5	$207.76	12.850%	$234.4572	$234.46	$234.45	$234.50
Purchase #6	$22.77	4.146%	$23.714	$23.71	$23.70	$23.70
Purchase #7	$141.38	6.518%	$150.5951	$150.60	$150.60	$150.60
7 purchase totals =	$754.93		$811.7135	$811.73	$811.65	$811.90