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	$14.73	4.355%	$15.3715	$15.37	$15.35	$15.40
Purchase #2	$115.43	6.726%	$123.1938	$123.19	$123.20	$123.20
Purchase #3	$16.89	11.800%	$18.883	$18.88	$18.90	$18.90
Purchase #4	$72.27	9.629%	$79.2289	$79.23	$79.25	$79.20
Purchase #5	$151.89	13.644%	$172.6139	$172.61	$172.60	$172.60
Purchase #6	$91.56	5.462%	$96.561	$96.56	$96.55	$96.60
Purchase #7	$24.71	6.148%	$26.2292	$26.23	$26.25	$26.20
7 purchase totals =	$487.48		$532.0813	$532.07	$532.10	$532.10