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	$53.29	10.825%	$59.0586	$59.06	$59.05	$59.10
Purchase #2	$192.71	6.133%	$204.5289	$204.53	$204.55	$204.50
Purchase #3	$201.83	12.701%	$227.4644	$227.46	$227.45	$227.50
Purchase #4	$127.30	12.187%	$142.8141	$142.81	$142.80	$142.80
Purchase #5	$242.47	5.290%	$255.2967	$255.30	$255.30	$255.30
Purchase #6	$27.65	13.722%	$31.4441	$31.44	$31.45	$31.40
Purchase #7	$85.71	4.342%	$89.4315	$89.43	$89.45	$89.40
7 purchase totals =	$930.96		$1,010.0383	$1,010.03	$1,010.05	$1,010.00