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	$83.70	4.176%	$87.1953	$87.20	$87.20	$87.20
Purchase #2	$79.85	10.380%	$88.1384	$88.14	$88.15	$88.10
Purchase #3	$233.76	10.374%	$258.0103	$258.01	$258.00	$258.00
Purchase #4	$240.66	6.166%	$255.4991	$255.50	$255.50	$255.50
Purchase #5	$43.35	3.473%	$44.8555	$44.86	$44.85	$44.90
Purchase #6	$178.37	12.439%	$200.5574	$200.56	$200.55	$200.60
Purchase #7	$228.46	4.564%	$238.8869	$238.89	$238.90	$238.90
7 purchase totals =	$1,088.15		$1,173.1429	$1,173.16	$1,173.15	$1,173.20