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	$191.40	4.660%	$200.3192	$200.32	$200.30	$200.30
Purchase #2	$249.47	3.309%	$257.725	$257.73	$257.75	$257.70
Purchase #3	$46.69	11.296%	$51.9641	$51.96	$51.95	$52.00
Purchase #4	$198.92	10.335%	$219.4784	$219.48	$219.50	$219.50
Purchase #5	$148.73	10.610%	$164.5103	$164.51	$164.50	$164.50
Purchase #6	$164.95	12.694%	$185.8888	$185.89	$185.90	$185.90
Purchase #7	$229.90	6.481%	$244.7998	$244.80	$244.80	$244.80
7 purchase totals =	$1,230.06		$1,324.6856	$1,324.69	$1,324.70	$1,324.70