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	$156.81	3.511%	$162.3156	$162.32	$162.30	$162.30
Purchase #2	$96.88	3.329%	$100.1051	$100.11	$100.10	$100.10
Purchase #3	$232.43	9.775%	$255.15	$255.15	$255.15	$255.20
Purchase #4	$218.25	10.595%	$241.3736	$241.37	$241.35	$241.40
Purchase #5	$39.72	11.776%	$44.3974	$44.40	$44.40	$44.40
Purchase #6	$54.25	4.592%	$56.7412	$56.74	$56.75	$56.70
Purchase #7	$33.42	13.145%	$37.8131	$37.81	$37.80	$37.80
7 purchase totals =	$831.76		$897.8960	$897.90	$897.85	$897.90