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	$64.30	5.339%	$67.733	$67.73	$67.75	$67.70
Purchase #2	$173.26	13.231%	$196.184	$196.18	$196.20	$196.20
Purchase #3	$84.43	9.660%	$92.5859	$92.59	$92.60	$92.60
Purchase #4	$38.48	5.636%	$40.6487	$40.65	$40.65	$40.60
Purchase #5	$37.49	11.528%	$41.8118	$41.81	$41.80	$41.80
Purchase #6	$90.61	11.794%	$101.2965	$101.30	$101.30	$101.30
Purchase #7	$52.71	5.128%	$55.413	$55.41	$55.40	$55.40
7 purchase totals =	$541.28		$595.6729	$595.67	$595.70	$595.60