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	$169.75	3.768%	$176.1462	$176.15	$176.15	$176.10
Purchase #2	$216.27	7.794%	$233.1261	$233.13	$233.15	$233.10
Purchase #3	$124.27	10.672%	$137.5321	$137.53	$137.55	$137.50
Purchase #4	$183.49	3.663%	$190.2112	$190.21	$190.20	$190.20
Purchase #5	$6.30	3.641%	$6.5294	$6.53	$6.55	$6.50
Purchase #6	$142.33	3.179%	$146.8547	$146.85	$146.85	$146.90
Purchase #7	$151.47	13.143%	$171.3777	$171.38	$171.40	$171.40
7 purchase totals =	$993.88		$1,061.7774	$1,061.78	$1,061.85	$1,061.70