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	$204.51	10.159%	$225.2862	$225.29	$225.30	$225.30
Purchase #2	$89.91	4.390%	$93.857	$93.86	$93.85	$93.90
Purchase #3	$91.76	12.181%	$102.9373	$102.94	$102.95	$102.90
Purchase #4	$219.31	6.282%	$233.0871	$233.09	$233.10	$233.10
Purchase #5	$163.86	8.686%	$178.0929	$178.09	$178.10	$178.10
Purchase #6	$113.71	12.308%	$127.7054	$127.71	$127.70	$127.70
Purchase #7	$9.69	8.126%	$10.4774	$10.48	$10.50	$10.50
7 purchase totals =	$892.75		$971.4433	$971.46	$971.50	$971.50