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	$122.66	3.709%	$127.2095	$127.21	$127.20	$127.20
Purchase #2	$187.63	4.816%	$196.6663	$196.67	$196.65	$196.70
Purchase #3	$196.53	11.840%	$219.7992	$219.80	$219.80	$219.80
Purchase #4	$160.34	11.526%	$178.8208	$178.82	$178.80	$178.80
Purchase #5	$215.56	8.465%	$233.8072	$233.81	$233.80	$233.80
Purchase #6	$62.60	11.220%	$69.6237	$69.62	$69.60	$69.60
Purchase #7	$95.46	13.661%	$108.5008	$108.50	$108.50	$108.50
7 purchase totals =	$1,040.78		$1,134.4275	$1,134.43	$1,134.35	$1,134.40