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	$43.31	4.790%	$45.3845	$45.38	$45.40	$45.40
Purchase #2	$33.77	9.443%	$36.9589	$36.96	$36.95	$37.00
Purchase #3	$6.81	13.767%	$7.7475	$7.75	$7.75	$7.70
Purchase #4	$167.30	7.194%	$179.3356	$179.34	$179.35	$179.30
Purchase #5	$124.26	3.451%	$128.5482	$128.55	$128.55	$128.50
Purchase #6	$58.86	9.630%	$64.5282	$64.53	$64.55	$64.50
Purchase #7	$49.49	8.584%	$53.7382	$53.74	$53.75	$53.70
7 purchase totals =	$483.80		$516.2411	$516.25	$516.30	$516.10