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	$127.51	4.312%	$133.0082	$133.01	$133.00	$133.00
Purchase #2	$64.32	5.597%	$67.92	$67.92	$67.90	$67.90
Purchase #3	$142.85	5.179%	$150.2482	$150.25	$150.25	$150.20
Purchase #4	$139.97	4.191%	$145.8361	$145.84	$145.85	$145.80
Purchase #5	$219.37	9.619%	$240.4712	$240.47	$240.45	$240.50
Purchase #6	$29.26	8.308%	$31.6909	$31.69	$31.70	$31.70
Purchase #7	$35.33	8.294%	$38.2603	$38.26	$38.25	$38.30
7 purchase totals =	$758.61		$807.4349	$807.44	$807.40	$807.40