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	$130.47	8.750%	$141.8861	$141.89	$141.90	$141.90
Purchase #2	$87.99	3.166%	$90.7758	$90.78	$90.80	$90.80
Purchase #3	$246.59	9.181%	$269.2294	$269.23	$269.25	$269.20
Purchase #4	$127.33	11.371%	$141.8087	$141.81	$141.80	$141.80
Purchase #5	$62.89	12.123%	$70.5142	$70.51	$70.50	$70.50
Purchase #6	$96.62	4.403%	$100.8742	$100.87	$100.85	$100.90
Purchase #7	$220.29	6.325%	$234.2233	$234.22	$234.20	$234.20
7 purchase totals =	$972.18		$1,049.3117	$1,049.31	$1,049.30	$1,049.30