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	$158.52	13.646%	$180.1516	$180.15	$180.15	$180.20
Purchase #2	$34.46	7.839%	$37.1613	$37.16	$37.15	$37.20
Purchase #3	$5.28	5.359%	$5.563	$5.56	$5.55	$5.60
Purchase #4	$127.41	13.239%	$144.2778	$144.28	$144.30	$144.30
Purchase #5	$175.58	5.718%	$185.6197	$185.62	$185.60	$185.60
Purchase #6	$115.42	3.714%	$119.7067	$119.71	$119.70	$119.70
Purchase #7	$185.38	4.293%	$193.3384	$193.34	$193.35	$193.30
7 purchase totals =	$802.05		$865.8185	$865.82	$865.80	$865.90