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	$40.90	10.835%	$45.3315	$45.33	$45.35	$45.30
Purchase #2	$100.44	3.195%	$103.6491	$103.65	$103.65	$103.60
Purchase #3	$115.61	7.125%	$123.8472	$123.85	$123.85	$123.80
Purchase #4	$149.94	13.547%	$170.2524	$170.25	$170.25	$170.30
Purchase #5	$201.76	3.373%	$208.5654	$208.57	$208.55	$208.60
Purchase #6	$69.44	4.526%	$72.5829	$72.58	$72.60	$72.60
Purchase #7	$113.91	6.662%	$121.4987	$121.50	$121.50	$121.50
7 purchase totals =	$792.00		$845.7272	$845.73	$845.75	$845.70