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	$49.56	6.622%	$52.8419	$52.84	$52.85	$52.80
Purchase #2	$90.50	9.195%	$98.8215	$98.82	$98.80	$98.80
Purchase #3	$10.90	10.552%	$12.0502	$12.05	$12.05	$12.10
Purchase #4	$46.75	8.399%	$50.6765	$50.68	$50.70	$50.70
Purchase #5	$141.84	11.719%	$158.4622	$158.46	$158.45	$158.50
Purchase #6	$212.73	3.819%	$220.8542	$220.85	$220.85	$220.90
Purchase #7	$180.27	11.449%	$200.9091	$200.91	$200.90	$200.90
7 purchase totals =	$732.55		$794.6156	$794.61	$794.60	$794.70