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	$33.83	12.182%	$37.9512	$37.95	$37.95	$38.00
Purchase #2	$227.93	7.610%	$245.2755	$245.28	$245.30	$245.30
Purchase #3	$230.97	11.253%	$256.9611	$256.96	$256.95	$257.00
Purchase #4	$96.39	3.613%	$99.8726	$99.87	$99.85	$99.90
Purchase #5	$170.72	5.131%	$179.4796	$179.48	$179.50	$179.50
Purchase #6	$248.86	13.685%	$282.9165	$282.92	$282.90	$282.90
Purchase #7	$6.67	9.333%	$7.2925	$7.29	$7.30	$7.30
7 purchase totals =	$1,015.37		$1,109.7490	$1,109.75	$1,109.75	$1,109.90