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	$185.54	5.481%	$195.7094	$195.71	$195.70	$195.70
Purchase #2	$150.36	5.286%	$158.308	$158.31	$158.30	$158.30
Purchase #3	$54.61	8.528%	$59.2671	$59.27	$59.25	$59.30
Purchase #4	$131.96	12.614%	$148.6054	$148.61	$148.60	$148.60
Purchase #5	$35.98	3.539%	$37.2533	$37.25	$37.25	$37.30
Purchase #6	$148.48	10.383%	$163.8967	$163.90	$163.90	$163.90
Purchase #7	$222.56	3.602%	$230.5766	$230.58	$230.60	$230.60
7 purchase totals =	$929.49		$993.6165	$993.63	$993.60	$993.70