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	$219.85	6.543%	$234.2348	$234.23	$234.25	$234.20
Purchase #2	$27.51	13.476%	$31.2172	$31.22	$31.20	$31.20
Purchase #3	$158.67	6.814%	$169.4818	$169.48	$169.50	$169.50
Purchase #4	$47.60	10.682%	$52.6846	$52.68	$52.70	$52.70
Purchase #5	$6.43	12.339%	$7.2234	$7.22	$7.20	$7.20
Purchase #6	$151.49	3.211%	$156.3543	$156.35	$156.35	$156.40
Purchase #7	$72.77	13.137%	$82.3298	$82.33	$82.35	$82.30
7 purchase totals =	$684.32		$733.5259	$733.51	$733.55	$733.50