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	$200.26	4.696%	$209.6642	$209.66	$209.65	$209.70
Purchase #2	$111.64	13.821%	$127.0698	$127.07	$127.05	$127.10
Purchase #3	$224.39	13.339%	$254.3214	$254.32	$254.30	$254.30
Purchase #4	$56.86	9.298%	$62.1468	$62.15	$62.15	$62.10
Purchase #5	$6.55	13.818%	$7.4551	$7.46	$7.45	$7.50
Purchase #6	$49.84	11.294%	$55.4689	$55.47	$55.45	$55.50
Purchase #7	$190.97	3.867%	$198.3548	$198.35	$198.35	$198.40
7 purchase totals =	$840.51		$914.4810	$914.48	$914.40	$914.60