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	$175.60	12.111%	$196.8669	$196.87	$196.85	$196.90
Purchase #2	$186.40	7.543%	$200.4602	$200.46	$200.45	$200.50
Purchase #3	$63.48	8.515%	$68.8853	$68.89	$68.90	$68.90
Purchase #4	$62.62	11.342%	$69.7224	$69.72	$69.70	$69.70
Purchase #5	$66.28	8.792%	$72.1073	$72.11	$72.10	$72.10
Purchase #6	$189.71	10.405%	$209.4493	$209.45	$209.45	$209.40
Purchase #7	$47.70	13.578%	$54.1767	$54.18	$54.20	$54.20
7 purchase totals =	$791.79		$871.6681	$871.68	$871.65	$871.70