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	$212.73	10.866%	$235.8452	$235.85	$235.85	$235.80
Purchase #2	$73.91	13.613%	$83.9714	$83.97	$83.95	$84.00
Purchase #3	$215.40	3.512%	$222.9648	$222.96	$222.95	$223.00
Purchase #4	$219.35	3.754%	$227.5844	$227.58	$227.60	$227.60
Purchase #5	$37.54	12.336%	$42.1709	$42.17	$42.15	$42.20
Purchase #6	$234.96	5.837%	$248.6746	$248.67	$248.65	$248.70
Purchase #7	$78.54	4.758%	$82.2769	$82.28	$82.30	$82.30
7 purchase totals =	$1,072.43		$1,143.4882	$1,143.48	$1,143.45	$1,143.60