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	$6.27	13.613%	$7.1235	$7.12	$7.10	$7.10
Purchase #2	$194.37	13.125%	$219.8811	$219.88	$219.90	$219.90
Purchase #3	$88.35	13.754%	$100.5017	$100.50	$100.50	$100.50
Purchase #4	$59.26	8.623%	$64.37	$64.37	$64.35	$64.40
Purchase #5	$47.50	4.749%	$49.7558	$49.76	$49.75	$49.80
Purchase #6	$147.83	7.766%	$159.3105	$159.31	$159.30	$159.30
Purchase #7	$17.48	5.613%	$18.4612	$18.46	$18.45	$18.50
7 purchase totals =	$561.06		$619.4038	$619.40	$619.35	$619.50