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	$184.88	6.421%	$196.7511	$196.75	$196.75	$196.80
Purchase #2	$207.44	4.827%	$217.4531	$217.45	$217.45	$217.50
Purchase #3	$93.48	6.531%	$99.5852	$99.59	$99.60	$99.60
Purchase #4	$78.65	10.859%	$87.1906	$87.19	$87.20	$87.20
Purchase #5	$54.82	11.601%	$61.1797	$61.18	$61.20	$61.20
Purchase #6	$175.73	10.723%	$194.5735	$194.57	$194.55	$194.60
Purchase #7	$218.92	8.141%	$236.7423	$236.74	$236.75	$236.70
7 purchase totals =	$1,013.92		$1,093.4755	$1,093.47	$1,093.50	$1,093.60