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	$218.68	10.136%	$240.8454	$240.85	$240.85	$240.80
Purchase #2	$213.66	11.551%	$238.3399	$238.34	$238.35	$238.30
Purchase #3	$222.48	6.427%	$236.7788	$236.78	$236.80	$236.80
Purchase #4	$124.89	5.353%	$131.5754	$131.58	$131.60	$131.60
Purchase #5	$168.64	13.607%	$191.5868	$191.59	$191.60	$191.60
Purchase #6	$52.46	3.775%	$54.4404	$54.44	$54.45	$54.40
Purchase #7	$77.84	12.499%	$87.5692	$87.57	$87.55	$87.60
7 purchase totals =	$1,078.65		$1,181.1359	$1,181.15	$1,181.20	$1,181.10