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	$32.64	9.403%	$35.7091	$35.71	$35.70	$35.70
Purchase #2	$213.95	5.549%	$225.8221	$225.82	$225.80	$225.80
Purchase #3	$92.37	7.539%	$99.3338	$99.33	$99.35	$99.30
Purchase #4	$119.74	9.174%	$130.7249	$130.72	$130.70	$130.70
Purchase #5	$180.60	4.790%	$189.2507	$189.25	$189.25	$189.30
Purchase #6	$105.82	9.702%	$116.0867	$116.09	$116.10	$116.10
Purchase #7	$170.78	3.421%	$176.6224	$176.62	$176.60	$176.60
7 purchase totals =	$915.90		$973.5497	$973.54	$973.50	$973.50