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	$208.29	4.351%	$217.3527	$217.35	$217.35	$217.40
Purchase #2	$115.80	6.365%	$123.1707	$123.17	$123.15	$123.20
Purchase #3	$42.64	11.716%	$47.6357	$47.64	$47.65	$47.60
Purchase #4	$152.38	9.697%	$167.1563	$167.16	$167.15	$167.20
Purchase #5	$224.46	9.526%	$245.8421	$245.84	$245.85	$245.80
Purchase #6	$81.74	10.747%	$90.5246	$90.52	$90.50	$90.50
Purchase #7	$185.26	4.727%	$194.0172	$194.02	$194.00	$194.00
7 purchase totals =	$1,010.57		$1,085.6993	$1,085.70	$1,085.65	$1,085.70