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	$79.79	4.696%	$83.5369	$83.54	$83.55	$83.50
Purchase #2	$24.88	13.869%	$28.3306	$28.33	$28.35	$28.30
Purchase #3	$116.81	10.434%	$128.998	$129.00	$129.00	$129.00
Purchase #4	$10.93	9.196%	$11.9351	$11.94	$11.95	$11.90
Purchase #5	$91.45	12.702%	$103.066	$103.07	$103.05	$103.10
Purchase #6	$78.53	6.162%	$83.369	$83.37	$83.35	$83.40
Purchase #7	$240.86	10.441%	$266.0082	$266.01	$266.00	$266.00
7 purchase totals =	$643.25		$705.2438	$705.26	$705.25	$705.20