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	$187.80	13.459%	$213.076	$213.08	$213.10	$213.10
Purchase #2	$30.83	5.797%	$32.6172	$32.62	$32.60	$32.60
Purchase #3	$74.50	10.857%	$82.5885	$82.59	$82.60	$82.60
Purchase #4	$81.53	9.821%	$89.5371	$89.54	$89.55	$89.50
Purchase #5	$73.80	4.517%	$77.1335	$77.13	$77.15	$77.10
Purchase #6	$94.55	5.870%	$100.1001	$100.10	$100.10	$100.10
Purchase #7	$151.47	10.361%	$167.1638	$167.16	$167.15	$167.20
7 purchase totals =	$694.48		$762.2162	$762.22	$762.25	$762.20