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	$79.27	7.616%	$85.3072	$85.31	$85.30	$85.30
Purchase #2	$182.60	3.256%	$188.5455	$188.55	$188.55	$188.50
Purchase #3	$193.99	13.227%	$219.6491	$219.65	$219.65	$219.60
Purchase #4	$248.44	5.860%	$262.9986	$263.00	$263.00	$263.00
Purchase #5	$170.38	3.564%	$176.4523	$176.45	$176.45	$176.50
Purchase #6	$78.69	10.186%	$86.7054	$86.71	$86.70	$86.70
Purchase #7	$118.42	11.371%	$131.8855	$131.89	$131.90	$131.90
7 purchase totals =	$1,071.79		$1,151.5436	$1,151.56	$1,151.55	$1,151.50