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	$184.80	6.499%	$196.8102	$196.81	$196.80	$196.80
Purchase #2	$220.42	10.163%	$242.8213	$242.82	$242.80	$242.80
Purchase #3	$61.59	11.189%	$68.4813	$68.48	$68.50	$68.50
Purchase #4	$219.62	13.514%	$249.2994	$249.30	$249.30	$249.30
Purchase #5	$222.64	9.278%	$243.2965	$243.30	$243.30	$243.30
Purchase #6	$39.40	5.190%	$41.4449	$41.44	$41.45	$41.40
Purchase #7	$29.93	11.181%	$33.2765	$33.28	$33.30	$33.30
7 purchase totals =	$978.40		$1,075.4301	$1,075.43	$1,075.45	$1,075.40