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	$127.35	4.361%	$132.9037	$132.90	$132.90	$132.90
Purchase #2	$142.45	9.541%	$156.0412	$156.04	$156.05	$156.00
Purchase #3	$59.96	7.809%	$64.6423	$64.64	$64.65	$64.60
Purchase #4	$215.37	4.766%	$225.6345	$225.63	$225.65	$225.60
Purchase #5	$179.50	6.867%	$191.8263	$191.83	$191.85	$191.80
Purchase #6	$21.91	6.528%	$23.3403	$23.34	$23.35	$23.30
Purchase #7	$160.93	6.555%	$171.479	$171.48	$171.50	$171.50
7 purchase totals =	$907.47		$965.8673	$965.86	$965.95	$965.70