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	$128.61	10.439%	$142.0356	$142.04	$142.05	$142.00
Purchase #2	$121.89	11.776%	$136.2438	$136.24	$136.25	$136.20
Purchase #3	$131.31	7.403%	$141.0309	$141.03	$141.05	$141.00
Purchase #4	$115.31	6.773%	$123.1199	$123.12	$123.10	$123.10
Purchase #5	$12.47	7.672%	$13.4267	$13.43	$13.45	$13.40
Purchase #6	$135.88	11.292%	$151.2236	$151.22	$151.20	$151.20
Purchase #7	$52.27	7.116%	$55.9895	$55.99	$56.00	$56.00
7 purchase totals =	$697.74		$763.0700	$763.07	$763.10	$762.90