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	$114.28	4.687%	$119.6363	$119.64	$119.65	$119.60
Purchase #2	$84.36	13.274%	$95.5579	$95.56	$95.55	$95.60
Purchase #3	$56.79	4.302%	$59.2331	$59.23	$59.25	$59.20
Purchase #4	$18.56	9.760%	$20.3715	$20.37	$20.35	$20.40
Purchase #5	$206.88	5.789%	$218.8563	$218.86	$218.85	$218.90
Purchase #6	$172.88	10.791%	$191.5355	$191.54	$191.55	$191.50
Purchase #7	$87.78	7.548%	$94.4056	$94.41	$94.40	$94.40
7 purchase totals =	$741.53		$799.5962	$799.61	$799.60	$799.60