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	$72.56	7.274%	$77.838	$77.84	$77.85	$77.80
Purchase #2	$161.87	6.207%	$171.9173	$171.92	$171.90	$171.90
Purchase #3	$140.38	3.149%	$144.8006	$144.80	$144.80	$144.80
Purchase #4	$94.71	5.873%	$100.2723	$100.27	$100.25	$100.30
Purchase #5	$234.69	11.475%	$261.6207	$261.62	$261.60	$261.60
Purchase #6	$175.47	12.146%	$196.7826	$196.78	$196.80	$196.80
Purchase #7	$95.95	12.313%	$107.7643	$107.76	$107.75	$107.80
7 purchase totals =	$975.63		$1,060.9958	$1,060.99	$1,060.95	$1,061.00