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	$87.98	7.423%	$94.5108	$94.51	$94.50	$94.50
Purchase #2	$88.87	13.117%	$100.5271	$100.53	$100.55	$100.50
Purchase #3	$187.69	8.169%	$203.0224	$203.02	$203.00	$203.00
Purchase #4	$242.32	11.666%	$270.5891	$270.59	$270.60	$270.60
Purchase #5	$114.71	10.667%	$126.9461	$126.95	$126.95	$126.90
Purchase #6	$201.63	5.217%	$212.149	$212.15	$212.15	$212.10
Purchase #7	$85.72	5.140%	$90.126	$90.13	$90.15	$90.10
7 purchase totals =	$1,008.92		$1,097.8705	$1,097.88	$1,097.90	$1,097.70