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	$223.78	3.317%	$231.2028	$231.20	$231.20	$231.20
Purchase #2	$94.38	7.554%	$101.5095	$101.51	$101.50	$101.50
Purchase #3	$67.94	6.753%	$72.528	$72.53	$72.55	$72.50
Purchase #4	$187.80	9.399%	$205.4513	$205.45	$205.45	$205.50
Purchase #5	$8.42	11.648%	$9.4008	$9.40	$9.40	$9.40
Purchase #6	$51.49	13.557%	$58.4705	$58.47	$58.45	$58.50
Purchase #7	$78.93	4.476%	$82.4629	$82.46	$82.45	$82.50
7 purchase totals =	$712.74		$761.0258	$761.02	$761.00	$761.10