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	$93.54	10.831%	$103.6713	$103.67	$103.65	$103.70
Purchase #2	$143.97	9.374%	$157.4657	$157.47	$157.45	$157.50
Purchase #3	$231.75	13.232%	$262.4152	$262.42	$262.40	$262.40
Purchase #4	$92.28	8.704%	$100.3121	$100.31	$100.30	$100.30
Purchase #5	$154.98	12.515%	$174.3757	$174.38	$174.40	$174.40
Purchase #6	$155.67	8.488%	$168.8833	$168.88	$168.90	$168.90
Purchase #7	$145.96	6.481%	$155.4197	$155.42	$155.40	$155.40
7 purchase totals =	$1,018.15		$1,122.5430	$1,122.55	$1,122.50	$1,122.60