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	$43.90	5.172%	$46.1705	$46.17	$46.15	$46.20
Purchase #2	$110.28	4.117%	$114.8202	$114.82	$114.80	$114.80
Purchase #3	$219.52	13.119%	$248.3188	$248.32	$248.30	$248.30
Purchase #4	$177.50	7.577%	$190.9492	$190.95	$190.95	$190.90
Purchase #5	$153.54	9.796%	$168.5808	$168.58	$168.60	$168.60
Purchase #6	$94.48	11.231%	$105.091	$105.09	$105.10	$105.10
Purchase #7	$115.54	12.506%	$129.9894	$129.99	$130.00	$130.00
7 purchase totals =	$914.76		$1,003.9199	$1,003.92	$1,003.90	$1,003.90