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	$64.77	4.288%	$67.5473	$67.55	$67.55	$67.50
Purchase #2	$82.84	3.703%	$85.9076	$85.91	$85.90	$85.90
Purchase #3	$223.91	10.134%	$246.601	$246.60	$246.60	$246.60
Purchase #4	$143.51	13.223%	$162.4863	$162.49	$162.50	$162.50
Purchase #5	$227.46	11.511%	$253.6429	$253.64	$253.65	$253.60
Purchase #6	$76.96	8.259%	$83.3161	$83.32	$83.30	$83.30
Purchase #7	$36.47	12.503%	$41.0298	$41.03	$41.05	$41.00
7 purchase totals =	$855.92		$940.5310	$940.54	$940.55	$940.40