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	$86.64	11.426%	$96.5395	$96.54	$96.55	$96.50
Purchase #2	$27.90	8.654%	$30.3145	$30.31	$30.30	$30.30
Purchase #3	$69.64	13.181%	$78.8192	$78.82	$78.80	$78.80
Purchase #4	$88.44	10.693%	$97.8969	$97.90	$97.90	$97.90
Purchase #5	$94.27	11.837%	$105.4287	$105.43	$105.45	$105.40
Purchase #6	$18.49	13.758%	$21.0339	$21.03	$21.05	$21.00
Purchase #7	$119.72	12.333%	$134.4851	$134.49	$134.50	$134.50
7 purchase totals =	$505.10		$564.5178	$564.52	$564.55	$564.40