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	$53.47	10.796%	$59.2426	$59.24	$59.25	$59.20
Purchase #2	$167.83	3.470%	$173.6537	$173.65	$173.65	$173.70
Purchase #3	$173.25	13.665%	$196.9246	$196.92	$196.90	$196.90
Purchase #4	$151.63	3.257%	$156.5686	$156.57	$156.55	$156.60
Purchase #5	$189.43	13.265%	$214.5579	$214.56	$214.55	$214.60
Purchase #6	$224.31	4.430%	$234.2469	$234.25	$234.25	$234.20
Purchase #7	$122.61	5.514%	$129.3707	$129.37	$129.35	$129.40
7 purchase totals =	$1,082.53		$1,164.5650	$1,164.56	$1,164.50	$1,164.60