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	$125.34	6.452%	$133.4269	$133.43	$133.45	$133.40
Purchase #2	$231.48	4.630%	$242.1975	$242.20	$242.20	$242.20
Purchase #3	$68.25	9.572%	$74.7829	$74.78	$74.80	$74.80
Purchase #4	$18.48	11.119%	$20.5348	$20.53	$20.55	$20.50
Purchase #5	$145.32	3.570%	$150.5079	$150.51	$150.50	$150.50
Purchase #6	$79.48	12.288%	$89.2465	$89.25	$89.25	$89.20
Purchase #7	$16.46	10.348%	$18.1633	$18.16	$18.15	$18.20
7 purchase totals =	$684.81		$728.8598	$728.86	$728.90	$728.80