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	$10.53	3.538%	$10.9026	$10.90	$10.90	$10.90
Purchase #2	$215.43	10.531%	$238.1169	$238.12	$238.10	$238.10
Purchase #3	$195.87	10.567%	$216.5676	$216.57	$216.55	$216.60
Purchase #4	$100.31	12.170%	$112.5177	$112.52	$112.50	$112.50
Purchase #5	$135.59	7.184%	$145.3308	$145.33	$145.35	$145.30
Purchase #6	$43.74	6.256%	$46.4764	$46.48	$46.50	$46.50
Purchase #7	$244.25	4.746%	$255.8421	$255.84	$255.85	$255.80
7 purchase totals =	$945.72		$1,025.7541	$1,025.76	$1,025.75	$1,025.70