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	$144.80	10.612%	$160.1662	$160.17	$160.15	$160.20
Purchase #2	$42.74	4.194%	$44.5325	$44.53	$44.55	$44.50
Purchase #3	$172.56	13.674%	$196.1559	$196.16	$196.15	$196.20
Purchase #4	$103.96	13.236%	$117.7201	$117.72	$117.70	$117.70
Purchase #5	$84.98	5.297%	$89.4814	$89.48	$89.50	$89.50
Purchase #6	$46.70	9.585%	$51.1762	$51.18	$51.20	$51.20
Purchase #7	$41.78	10.669%	$46.2375	$46.24	$46.25	$46.20
7 purchase totals =	$637.52		$705.4698	$705.48	$705.50	$705.50