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	$103.82	11.406%	$115.6617	$115.66	$115.65	$115.70
Purchase #2	$68.56	6.276%	$72.8628	$72.86	$72.85	$72.90
Purchase #3	$198.29	6.358%	$210.8973	$210.90	$210.90	$210.90
Purchase #4	$107.82	6.614%	$114.9512	$114.95	$114.95	$115.00
Purchase #5	$173.66	7.661%	$186.9641	$186.96	$186.95	$187.00
Purchase #6	$222.93	8.711%	$242.3494	$242.35	$242.35	$242.30
Purchase #7	$54.25	9.725%	$59.5258	$59.53	$59.55	$59.50
7 purchase totals =	$929.33		$1,003.2123	$1,003.21	$1,003.20	$1,003.30