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	$157.93	8.811%	$171.8452	$171.85	$171.85	$171.80
Purchase #2	$227.69	10.630%	$251.8934	$251.89	$251.90	$251.90
Purchase #3	$101.31	11.410%	$112.8695	$112.87	$112.85	$112.90
Purchase #4	$209.39	6.789%	$223.6055	$223.61	$223.60	$223.60
Purchase #5	$204.88	10.206%	$225.7901	$225.79	$225.80	$225.80
Purchase #6	$89.74	9.862%	$98.5902	$98.59	$98.60	$98.60
Purchase #7	$170.99	9.157%	$186.6476	$186.65	$186.65	$186.60
7 purchase totals =	$1,161.93		$1,271.2415	$1,271.25	$1,271.25	$1,271.20