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	$178.55	10.551%	$197.3888	$197.39	$197.40	$197.40
Purchase #2	$114.81	7.425%	$123.3346	$123.33	$123.35	$123.30
Purchase #3	$167.74	12.746%	$189.1201	$189.12	$189.10	$189.10
Purchase #4	$88.82	12.510%	$99.9314	$99.93	$99.95	$99.90
Purchase #5	$88.50	10.868%	$98.1182	$98.12	$98.10	$98.10
Purchase #6	$78.81	10.345%	$86.9629	$86.96	$86.95	$87.00
Purchase #7	$197.35	5.564%	$208.3306	$208.33	$208.35	$208.30
7 purchase totals =	$914.58		$1,003.1866	$1,003.18	$1,003.20	$1,003.10