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	$78.82	13.557%	$89.5056	$89.51	$89.50	$89.50
Purchase #2	$183.86	6.648%	$196.083	$196.08	$196.10	$196.10
Purchase #3	$206.98	7.521%	$222.547	$222.55	$222.55	$222.50
Purchase #4	$35.39	6.690%	$37.7576	$37.76	$37.75	$37.80
Purchase #5	$195.32	11.302%	$217.3951	$217.40	$217.40	$217.40
Purchase #6	$86.57	7.564%	$93.1182	$93.12	$93.10	$93.10
Purchase #7	$234.40	13.306%	$265.5893	$265.59	$265.60	$265.60
7 purchase totals =	$1,021.34		$1,121.9958	$1,122.01	$1,122.00	$1,122.00