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	$166.76	7.524%	$179.307	$179.31	$179.30	$179.30
Purchase #2	$110.52	11.730%	$123.484	$123.48	$123.50	$123.50
Purchase #3	$233.32	12.650%	$262.835	$262.84	$262.85	$262.80
Purchase #4	$214.98	3.763%	$223.0697	$223.07	$223.05	$223.10
Purchase #5	$99.45	12.598%	$111.9787	$111.98	$112.00	$112.00
Purchase #6	$222.48	10.822%	$246.5568	$246.56	$246.55	$246.60
Purchase #7	$42.66	12.567%	$48.0211	$48.02	$48.00	$48.00
7 purchase totals =	$1,090.17		$1,195.2523	$1,195.26	$1,195.25	$1,195.30