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	$63.80	7.318%	$68.4689	$68.47	$68.45	$68.50
Purchase #2	$118.48	7.772%	$127.6883	$127.69	$127.70	$127.70
Purchase #3	$34.55	11.641%	$38.572	$38.57	$38.55	$38.60
Purchase #4	$158.88	13.736%	$180.7038	$180.70	$180.70	$180.70
Purchase #5	$99.82	8.752%	$108.5562	$108.56	$108.55	$108.60
Purchase #6	$100.64	4.222%	$104.889	$104.89	$104.90	$104.90
Purchase #7	$131.58	7.553%	$141.5182	$141.52	$141.50	$141.50
7 purchase totals =	$707.75		$770.3964	$770.40	$770.35	$770.50