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	$102.96	8.600%	$111.8146	$111.81	$111.80	$111.80
Purchase #2	$215.71	10.598%	$238.5709	$238.57	$238.55	$238.60
Purchase #3	$58.86	11.278%	$65.4982	$65.50	$65.50	$65.50
Purchase #4	$210.63	8.837%	$229.2434	$229.24	$229.25	$229.20
Purchase #5	$94.41	5.158%	$99.2797	$99.28	$99.30	$99.30
Purchase #6	$205.50	8.355%	$222.6695	$222.67	$222.65	$222.70
Purchase #7	$199.34	8.732%	$216.7464	$216.75	$216.75	$216.70
7 purchase totals =	$1,087.41		$1,183.8227	$1,183.82	$1,183.80	$1,183.80