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	$142.85	6.139%	$151.6196	$151.62	$151.60	$151.60
Purchase #2	$93.59	12.262%	$105.066	$105.07	$105.05	$105.10
Purchase #3	$113.28	6.653%	$120.8165	$120.82	$120.80	$120.80
Purchase #4	$192.96	12.312%	$216.7172	$216.72	$216.70	$216.70
Purchase #5	$82.87	11.314%	$92.2459	$92.25	$92.25	$92.20
Purchase #6	$34.60	4.787%	$36.2563	$36.26	$36.25	$36.30
Purchase #7	$6.78	12.283%	$7.6128	$7.61	$7.60	$7.60
7 purchase totals =	$666.93		$730.3343	$730.35	$730.25	$730.30