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	$83.51	3.200%	$86.1823	$86.18	$86.20	$86.20
Purchase #2	$196.33	4.344%	$204.8586	$204.86	$204.85	$204.90
Purchase #3	$128.34	11.349%	$142.9053	$142.91	$142.90	$142.90
Purchase #4	$43.49	8.480%	$47.178	$47.18	$47.20	$47.20
Purchase #5	$157.62	9.595%	$172.7436	$172.74	$172.75	$172.70
Purchase #6	$184.61	6.191%	$196.0392	$196.04	$196.05	$196.00
Purchase #7	$44.25	3.705%	$45.8895	$45.89	$45.90	$45.90
7 purchase totals =	$838.15		$895.7965	$895.80	$895.85	$895.80