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	$79.83	13.404%	$90.5304	$90.53	$90.55	$90.50
Purchase #2	$73.69	6.873%	$78.7547	$78.75	$78.75	$78.80
Purchase #3	$140.49	3.485%	$145.3861	$145.39	$145.40	$145.40
Purchase #4	$200.88	7.839%	$216.627	$216.63	$216.65	$216.60
Purchase #5	$241.83	5.585%	$255.3362	$255.34	$255.35	$255.30
Purchase #6	$40.63	7.106%	$43.5172	$43.52	$43.50	$43.50
Purchase #7	$226.52	7.599%	$243.7333	$243.73	$243.75	$243.70
7 purchase totals =	$1,003.87		$1,073.8849	$1,073.89	$1,073.95	$1,073.80