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	$175.54	7.822%	$189.2707	$189.27	$189.25	$189.30
Purchase #2	$33.95	12.183%	$38.0861	$38.09	$38.10	$38.10
Purchase #3	$22.60	7.282%	$24.2457	$24.25	$24.25	$24.20
Purchase #4	$96.55	13.427%	$109.5138	$109.51	$109.50	$109.50
Purchase #5	$28.52	11.676%	$31.85	$31.85	$31.85	$31.90
Purchase #6	$34.81	4.440%	$36.3556	$36.36	$36.35	$36.40
Purchase #7	$40.41	12.302%	$45.3812	$45.38	$45.40	$45.40
7 purchase totals =	$432.38		$474.7031	$474.71	$474.70	$474.80