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	$188.85	11.345%	$210.275	$210.28	$210.30	$210.30
Purchase #2	$147.80	6.398%	$157.2562	$157.26	$157.25	$157.30
Purchase #3	$54.81	8.177%	$59.2918	$59.29	$59.30	$59.30
Purchase #4	$20.29	9.457%	$22.2088	$22.21	$22.20	$22.20
Purchase #5	$226.92	11.871%	$253.8577	$253.86	$253.85	$253.90
Purchase #6	$246.85	13.789%	$280.8881	$280.89	$280.90	$280.90
Purchase #7	$154.97	12.443%	$174.2529	$174.25	$174.25	$174.30
7 purchase totals =	$1,040.49		$1,158.0305	$1,158.04	$1,158.05	$1,158.20