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	$42.55	6.789%	$45.4387	$45.44	$45.45	$45.40
Purchase #2	$130.32	13.516%	$147.9341	$147.93	$147.95	$147.90
Purchase #3	$51.67	13.798%	$58.7994	$58.80	$58.80	$58.80
Purchase #4	$179.38	9.532%	$196.4785	$196.48	$196.50	$196.50
Purchase #5	$52.37	6.857%	$55.961	$55.96	$55.95	$56.00
Purchase #6	$168.70	12.112%	$189.1329	$189.13	$189.15	$189.10
Purchase #7	$66.79	9.686%	$73.2593	$73.26	$73.25	$73.30
7 purchase totals =	$691.78		$767.0039	$767.00	$767.05	$767.00