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	$85.77	8.337%	$92.9206	$92.92	$92.90	$92.90
Purchase #2	$178.27	6.169%	$189.2675	$189.27	$189.25	$189.30
Purchase #3	$72.83	8.395%	$78.9441	$78.94	$78.95	$78.90
Purchase #4	$37.32	13.367%	$42.3086	$42.31	$42.30	$42.30
Purchase #5	$175.65	11.817%	$196.4066	$196.41	$196.40	$196.40
Purchase #6	$248.94	3.477%	$257.5956	$257.60	$257.60	$257.60
Purchase #7	$107.99	7.485%	$116.0731	$116.07	$116.05	$116.10
7 purchase totals =	$906.77		$973.5161	$973.52	$973.45	$973.50