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	$146.75	10.402%	$162.0149	$162.01	$162.00	$162.00
Purchase #2	$246.57	3.731%	$255.7695	$255.77	$255.75	$255.80
Purchase #3	$32.80	11.313%	$36.5107	$36.51	$36.50	$36.50
Purchase #4	$183.39	3.353%	$189.5391	$189.54	$189.55	$189.50
Purchase #5	$208.50	13.698%	$237.0603	$237.06	$237.05	$237.10
Purchase #6	$61.33	4.859%	$64.31	$64.31	$64.30	$64.30
Purchase #7	$85.38	5.654%	$90.2074	$90.21	$90.20	$90.20
7 purchase totals =	$964.72		$1,035.4119	$1,035.41	$1,035.35	$1,035.40