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	$191.53	9.715%	$210.1371	$210.14	$210.15	$210.10
Purchase #2	$44.53	6.645%	$47.489	$47.49	$47.50	$47.50
Purchase #3	$208.67	3.347%	$215.6542	$215.65	$215.65	$215.70
Purchase #4	$83.78	8.158%	$90.6148	$90.61	$90.60	$90.60
Purchase #5	$12.34	7.712%	$13.2917	$13.29	$13.30	$13.30
Purchase #6	$132.98	7.282%	$142.6636	$142.66	$142.65	$142.70
Purchase #7	$129.82	11.256%	$144.4325	$144.43	$144.45	$144.40
7 purchase totals =	$803.65		$864.2829	$864.27	$864.30	$864.30