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	$74.27	10.497%	$82.0661	$82.07	$82.05	$82.10
Purchase #2	$214.57	13.687%	$243.9382	$243.94	$243.95	$243.90
Purchase #3	$85.71	7.645%	$92.2625	$92.26	$92.25	$92.30
Purchase #4	$114.91	3.571%	$119.0134	$119.01	$119.00	$119.00
Purchase #5	$146.34	12.544%	$164.6969	$164.70	$164.70	$164.70
Purchase #6	$188.37	12.429%	$211.7825	$211.78	$211.80	$211.80
Purchase #7	$136.32	8.377%	$147.7395	$147.74	$147.75	$147.70
7 purchase totals =	$960.49		$1,061.4991	$1,061.50	$1,061.50	$1,061.50