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	$29.93	10.706%	$33.1343	$33.13	$33.15	$33.10
Purchase #2	$241.48	10.250%	$266.2317	$266.23	$266.25	$266.20
Purchase #3	$246.45	3.258%	$254.4793	$254.48	$254.50	$254.50
Purchase #4	$158.81	13.459%	$180.1842	$180.18	$180.20	$180.20
Purchase #5	$40.37	6.716%	$43.0812	$43.08	$43.10	$43.10
Purchase #6	$209.63	9.606%	$229.7671	$229.77	$229.75	$229.80
Purchase #7	$83.74	8.541%	$90.8922	$90.89	$90.90	$90.90
7 purchase totals =	$1,010.41		$1,097.7700	$1,097.76	$1,097.85	$1,097.80