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	$202.30	6.709%	$215.8723	$215.87	$215.85	$215.90
Purchase #2	$50.34	8.268%	$54.5021	$54.50	$54.50	$54.50
Purchase #3	$64.25	13.565%	$72.9655	$72.97	$72.95	$73.00
Purchase #4	$151.69	4.841%	$159.0333	$159.03	$159.05	$159.00
Purchase #5	$155.44	3.135%	$160.313	$160.31	$160.30	$160.30
Purchase #6	$160.44	12.343%	$180.2431	$180.24	$180.25	$180.20
Purchase #7	$234.25	12.142%	$262.6926	$262.69	$262.70	$262.70
7 purchase totals =	$1,018.71		$1,105.6219	$1,105.61	$1,105.60	$1,105.60