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	$203.63	6.672%	$217.2162	$217.22	$217.20	$217.20
Purchase #2	$123.52	6.323%	$131.3302	$131.33	$131.35	$131.30
Purchase #3	$181.43	5.108%	$190.6974	$190.70	$190.70	$190.70
Purchase #4	$196.32	8.697%	$213.394	$213.39	$213.40	$213.40
Purchase #5	$143.40	7.158%	$153.6646	$153.66	$153.65	$153.70
Purchase #6	$67.29	6.842%	$71.894	$71.89	$71.90	$71.90
Purchase #7	$176.74	5.581%	$186.6039	$186.60	$186.60	$186.60
7 purchase totals =	$1,092.33		$1,164.8003	$1,164.79	$1,164.80	$1,164.80