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	$179.66	9.585%	$196.8804	$196.88	$196.90	$196.90
Purchase #2	$32.80	5.368%	$34.5607	$34.56	$34.55	$34.60
Purchase #3	$49.89	12.841%	$56.2964	$56.30	$56.30	$56.30
Purchase #4	$117.36	11.285%	$130.6041	$130.60	$130.60	$130.60
Purchase #5	$237.54	7.513%	$255.3864	$255.39	$255.40	$255.40
Purchase #6	$196.34	7.723%	$211.5033	$211.50	$211.50	$211.50
Purchase #7	$222.76	6.484%	$237.2038	$237.20	$237.20	$237.20
7 purchase totals =	$1,036.35		$1,122.4351	$1,122.43	$1,122.45	$1,122.50