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	$159.67	7.460%	$171.5814	$171.58	$171.60	$171.60
Purchase #2	$165.71	12.659%	$186.6872	$186.69	$186.70	$186.70
Purchase #3	$28.65	10.279%	$31.5949	$31.59	$31.60	$31.60
Purchase #4	$146.94	13.155%	$166.27	$166.27	$166.25	$166.30
Purchase #5	$56.32	6.404%	$59.9267	$59.93	$59.95	$59.90
Purchase #6	$229.77	13.444%	$260.6603	$260.66	$260.65	$260.70
Purchase #7	$83.94	8.845%	$91.3645	$91.36	$91.35	$91.40
7 purchase totals =	$871.00		$968.0850	$968.08	$968.10	$968.20