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	$240.53	8.699%	$261.4537	$261.45	$261.45	$261.50
Purchase #2	$232.41	11.121%	$258.2563	$258.26	$258.25	$258.30
Purchase #3	$98.50	5.445%	$103.8633	$103.86	$103.85	$103.90
Purchase #4	$47.87	13.438%	$54.3028	$54.30	$54.30	$54.30
Purchase #5	$118.76	5.678%	$125.5032	$125.50	$125.50	$125.50
Purchase #6	$44.82	12.297%	$50.3315	$50.33	$50.35	$50.30
Purchase #7	$142.96	11.856%	$159.9093	$159.91	$159.90	$159.90
7 purchase totals =	$925.85		$1,013.6201	$1,013.61	$1,013.60	$1,013.70