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	$43.71	4.736%	$45.7801	$45.78	$45.80	$45.80
Purchase #2	$29.34	5.699%	$31.0121	$31.01	$31.00	$31.00
Purchase #3	$200.37	11.311%	$223.0339	$223.03	$223.05	$223.00
Purchase #4	$172.82	10.796%	$191.4776	$191.48	$191.50	$191.50
Purchase #5	$55.48	5.737%	$58.6629	$58.66	$58.65	$58.70
Purchase #6	$187.85	10.329%	$207.253	$207.25	$207.25	$207.30
Purchase #7	$32.70	13.617%	$37.1528	$37.15	$37.15	$37.20
7 purchase totals =	$722.27		$794.3724	$794.36	$794.40	$794.50