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	$123.31	3.244%	$127.3102	$127.31	$127.30	$127.30
Purchase #2	$63.47	7.114%	$67.9853	$67.99	$68.00	$68.00
Purchase #3	$218.78	11.127%	$243.1237	$243.12	$243.10	$243.10
Purchase #4	$167.35	3.141%	$172.6065	$172.61	$172.60	$172.60
Purchase #5	$100.27	5.182%	$105.466	$105.47	$105.45	$105.50
Purchase #6	$102.45	3.805%	$106.3482	$106.35	$106.35	$106.30
Purchase #7	$99.85	13.565%	$113.3947	$113.39	$113.40	$113.40
7 purchase totals =	$875.48		$936.2346	$936.24	$936.20	$936.20