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	$61.60	9.590%	$67.5074	$67.51	$67.50	$67.50
Purchase #2	$189.97	9.791%	$208.57	$208.57	$208.55	$208.60
Purchase #3	$153.28	8.648%	$166.5357	$166.54	$166.55	$166.50
Purchase #4	$153.54	11.824%	$171.6946	$171.69	$171.70	$171.70
Purchase #5	$131.36	9.562%	$143.9206	$143.92	$143.90	$143.90
Purchase #6	$180.37	11.244%	$200.6508	$200.65	$200.65	$200.70
Purchase #7	$216.72	9.673%	$237.6833	$237.68	$237.70	$237.70
7 purchase totals =	$1,086.84		$1,196.5624	$1,196.56	$1,196.55	$1,196.60