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	$205.28	3.596%	$212.6619	$212.66	$212.65	$212.70
Purchase #2	$120.90	8.748%	$131.4763	$131.48	$131.50	$131.50
Purchase #3	$49.66	11.543%	$55.3923	$55.39	$55.40	$55.40
Purchase #4	$53.69	10.834%	$59.5068	$59.51	$59.50	$59.50
Purchase #5	$16.89	8.784%	$18.3736	$18.37	$18.35	$18.40
Purchase #6	$178.34	5.278%	$187.7528	$187.75	$187.75	$187.80
Purchase #7	$89.69	8.842%	$97.6204	$97.62	$97.60	$97.60
7 purchase totals =	$714.45		$762.7841	$762.78	$762.75	$762.90