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	$141.73	11.198%	$157.6009	$157.60	$157.60	$157.60
Purchase #2	$41.71	8.548%	$45.2754	$45.28	$45.30	$45.30
Purchase #3	$111.89	8.351%	$121.2339	$121.23	$121.25	$121.20
Purchase #4	$240.47	12.856%	$271.3848	$271.38	$271.40	$271.40
Purchase #5	$80.46	3.728%	$83.4595	$83.46	$83.45	$83.50
Purchase #6	$200.42	12.192%	$224.8552	$224.86	$224.85	$224.90
Purchase #7	$229.78	13.410%	$260.5935	$260.59	$260.60	$260.60
7 purchase totals =	$1,046.46		$1,164.4032	$1,164.40	$1,164.45	$1,164.50