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	$102.88	10.451%	$113.632	$113.63	$113.65	$113.60
Purchase #2	$37.97	12.690%	$42.7884	$42.79	$42.80	$42.80
Purchase #3	$216.64	4.225%	$225.793	$225.79	$225.80	$225.80
Purchase #4	$114.73	4.157%	$119.4993	$119.50	$119.50	$119.50
Purchase #5	$102.53	13.654%	$116.5294	$116.53	$116.55	$116.50
Purchase #6	$235.41	7.666%	$253.4565	$253.46	$253.45	$253.50
Purchase #7	$76.29	5.543%	$80.5188	$80.52	$80.50	$80.50
7 purchase totals =	$886.45		$952.2174	$952.22	$952.25	$952.20