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	$92.71	7.450%	$99.6169	$99.62	$99.60	$99.60
Purchase #2	$73.49	12.505%	$82.6799	$82.68	$82.70	$82.70
Purchase #3	$88.43	4.193%	$92.1379	$92.14	$92.15	$92.10
Purchase #4	$55.43	7.484%	$59.5784	$59.58	$59.60	$59.60
Purchase #5	$88.94	8.104%	$96.1477	$96.15	$96.15	$96.10
Purchase #6	$206.38	7.674%	$222.2176	$222.22	$222.20	$222.20
Purchase #7	$208.25	4.797%	$218.2398	$218.24	$218.25	$218.20
7 purchase totals =	$813.63		$870.6182	$870.63	$870.65	$870.50