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	$173.94	13.754%	$197.8637	$197.86	$197.85	$197.90
Purchase #2	$133.47	8.139%	$144.3331	$144.33	$144.35	$144.30
Purchase #3	$112.47	10.118%	$123.8497	$123.85	$123.85	$123.80
Purchase #4	$79.44	12.511%	$89.3787	$89.38	$89.40	$89.40
Purchase #5	$88.35	5.200%	$92.9442	$92.94	$92.95	$92.90
Purchase #6	$234.33	11.350%	$260.9265	$260.93	$260.95	$260.90
Purchase #7	$173.36	7.242%	$185.9147	$185.91	$185.90	$185.90
7 purchase totals =	$995.36		$1,095.2106	$1,095.20	$1,095.25	$1,095.10