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	$99.45	5.692%	$105.1107	$105.11	$105.10	$105.10
Purchase #2	$185.30	5.874%	$196.1845	$196.18	$196.20	$196.20
Purchase #3	$226.32	4.441%	$236.3709	$236.37	$236.35	$236.40
Purchase #4	$48.39	3.803%	$50.2303	$50.23	$50.25	$50.20
Purchase #5	$12.96	7.501%	$13.9321	$13.93	$13.95	$13.90
Purchase #6	$152.30	3.253%	$157.2543	$157.25	$157.25	$157.30
Purchase #7	$88.41	7.826%	$95.329	$95.33	$95.35	$95.30
7 purchase totals =	$813.13		$854.4118	$854.40	$854.45	$854.40