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	$142.82	6.324%	$151.8519	$151.85	$151.85	$151.90
Purchase #2	$123.62	6.332%	$131.4476	$131.45	$131.45	$131.40
Purchase #3	$25.78	6.618%	$27.4861	$27.49	$27.50	$27.50
Purchase #4	$115.44	6.466%	$122.9044	$122.90	$122.90	$122.90
Purchase #5	$242.25	5.635%	$255.9008	$255.90	$255.90	$255.90
Purchase #6	$227.72	3.701%	$236.1479	$236.15	$236.15	$236.10
Purchase #7	$78.36	5.298%	$82.5115	$82.51	$82.50	$82.50
7 purchase totals =	$955.99		$1,008.2502	$1,008.25	$1,008.25	$1,008.20