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	$164.50	11.488%	$183.3978	$183.40	$183.40	$183.40
Purchase #2	$40.94	4.177%	$42.6501	$42.65	$42.65	$42.70
Purchase #3	$22.80	12.555%	$25.6625	$25.66	$25.65	$25.70
Purchase #4	$76.38	12.499%	$85.9267	$85.93	$85.95	$85.90
Purchase #5	$83.72	3.484%	$86.6368	$86.64	$86.65	$86.60
Purchase #6	$67.38	13.265%	$76.318	$76.32	$76.30	$76.30
Purchase #7	$19.57	13.780%	$22.2667	$22.27	$22.25	$22.30
7 purchase totals =	$475.29		$522.8586	$522.87	$522.85	$522.90