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	$93.59	5.222%	$98.4773	$98.48	$98.50	$98.50
Purchase #2	$159.69	13.563%	$181.3488	$181.35	$181.35	$181.30
Purchase #3	$227.98	5.661%	$240.8859	$240.89	$240.90	$240.90
Purchase #4	$98.51	3.530%	$101.9874	$101.99	$102.00	$102.00
Purchase #5	$193.59	10.661%	$214.2286	$214.23	$214.25	$214.20
Purchase #6	$187.79	4.754%	$196.7175	$196.72	$196.70	$196.70
Purchase #7	$30.26	5.781%	$32.0093	$32.01	$32.00	$32.00
7 purchase totals =	$991.41		$1,065.6548	$1,065.67	$1,065.70	$1,065.60