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	$208.83	5.432%	$220.1736	$220.17	$220.15	$220.20
Purchase #2	$196.60	11.334%	$218.8826	$218.88	$218.90	$218.90
Purchase #3	$53.46	7.213%	$57.3161	$57.32	$57.30	$57.30
Purchase #4	$171.83	4.231%	$179.1001	$179.10	$179.10	$179.10
Purchase #5	$157.43	9.519%	$172.4158	$172.42	$172.40	$172.40
Purchase #6	$108.57	13.550%	$123.2812	$123.28	$123.30	$123.30
Purchase #7	$133.59	12.221%	$149.916	$149.92	$149.90	$149.90
7 purchase totals =	$1,030.31		$1,121.0854	$1,121.09	$1,121.05	$1,121.10