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	$236.31	4.328%	$246.5375	$246.54	$246.55	$246.50
Purchase #2	$16.38	11.294%	$18.23	$18.23	$18.25	$18.20
Purchase #3	$175.28	7.202%	$187.9037	$187.90	$187.90	$187.90
Purchase #4	$134.98	6.793%	$144.1492	$144.15	$144.15	$144.10
Purchase #5	$190.70	12.759%	$215.0314	$215.03	$215.05	$215.00
Purchase #6	$31.30	12.761%	$35.2942	$35.29	$35.30	$35.30
Purchase #7	$86.41	4.325%	$90.1472	$90.15	$90.15	$90.10
7 purchase totals =	$871.36		$937.2932	$937.29	$937.35	$937.10