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	$85.51	10.187%	$94.2209	$94.22	$94.20	$94.20
Purchase #2	$179.71	9.543%	$196.8597	$196.86	$196.85	$196.90
Purchase #3	$218.59	10.288%	$241.0785	$241.08	$241.10	$241.10
Purchase #4	$172.64	4.333%	$180.1205	$180.12	$180.10	$180.10
Purchase #5	$6.91	10.490%	$7.6349	$7.63	$7.65	$7.60
Purchase #6	$179.79	7.429%	$193.1466	$193.15	$193.15	$193.10
Purchase #7	$103.98	13.593%	$118.114	$118.11	$118.10	$118.10
7 purchase totals =	$947.13		$1,031.1751	$1,031.17	$1,031.15	$1,031.10