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	$103.41	12.306%	$116.1356	$116.14	$116.15	$116.10
Purchase #2	$160.61	12.209%	$180.2189	$180.22	$180.20	$180.20
Purchase #3	$156.96	4.603%	$164.1849	$164.18	$164.20	$164.20
Purchase #4	$102.82	7.553%	$110.586	$110.59	$110.60	$110.60
Purchase #5	$63.68	11.800%	$71.1942	$71.19	$71.20	$71.20
Purchase #6	$42.82	5.359%	$45.1147	$45.11	$45.10	$45.10
Purchase #7	$243.95	8.570%	$264.8565	$264.86	$264.85	$264.90
7 purchase totals =	$874.25		$952.2908	$952.29	$952.30	$952.30