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	$238.32	7.586%	$256.399	$256.40	$256.40	$256.40
Purchase #2	$52.69	12.571%	$59.3137	$59.31	$59.30	$59.30
Purchase #3	$58.59	4.285%	$61.1006	$61.10	$61.10	$61.10
Purchase #4	$225.50	3.692%	$233.8255	$233.83	$233.85	$233.80
Purchase #5	$19.57	12.732%	$22.0617	$22.06	$22.05	$22.10
Purchase #6	$107.80	5.504%	$113.7333	$113.73	$113.75	$113.70
Purchase #7	$233.59	11.432%	$260.294	$260.29	$260.30	$260.30
7 purchase totals =	$936.06		$1,006.7278	$1,006.72	$1,006.75	$1,006.70