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	$136.89	5.221%	$144.037	$144.04	$144.05	$144.00
Purchase #2	$117.32	10.517%	$129.6585	$129.66	$129.65	$129.70
Purchase #3	$160.97	10.870%	$178.4674	$178.47	$178.45	$178.50
Purchase #4	$123.56	6.174%	$131.1886	$131.19	$131.20	$131.20
Purchase #5	$60.42	9.154%	$65.9508	$65.95	$65.95	$66.00
Purchase #6	$151.60	9.796%	$166.4507	$166.45	$166.45	$166.50
Purchase #7	$173.56	13.481%	$196.9576	$196.96	$196.95	$197.00
7 purchase totals =	$924.32		$1,012.7106	$1,012.72	$1,012.70	$1,012.90