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	$31.61	6.441%	$33.646	$33.65	$33.65	$33.60
Purchase #2	$123.29	5.807%	$130.4495	$130.45	$130.45	$130.40
Purchase #3	$188.94	10.568%	$208.9072	$208.91	$208.90	$208.90
Purchase #4	$123.96	8.753%	$134.8102	$134.81	$134.80	$134.80
Purchase #5	$171.76	11.552%	$191.6017	$191.60	$191.60	$191.60
Purchase #6	$12.45	12.321%	$13.984	$13.98	$14.00	$14.00
Purchase #7	$79.42	13.151%	$89.8645	$89.86	$89.85	$89.90
7 purchase totals =	$731.43		$803.2631	$803.26	$803.25	$803.20