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	$109.44	3.834%	$113.6359	$113.64	$113.65	$113.60
Purchase #2	$222.97	10.401%	$246.1611	$246.16	$246.15	$246.20
Purchase #3	$198.82	9.816%	$218.3362	$218.34	$218.35	$218.30
Purchase #4	$219.83	10.304%	$242.4813	$242.48	$242.50	$242.50
Purchase #5	$116.65	3.195%	$120.377	$120.38	$120.40	$120.40
Purchase #6	$89.67	5.678%	$94.7615	$94.76	$94.75	$94.80
Purchase #7	$90.75	5.407%	$95.6569	$95.66	$95.65	$95.70
7 purchase totals =	$1,048.13		$1,131.4099	$1,131.42	$1,131.45	$1,131.50