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	$202.31	4.259%	$210.9264	$210.93	$210.95	$210.90
Purchase #2	$102.96	10.407%	$113.675	$113.68	$113.70	$113.70
Purchase #3	$67.27	4.138%	$70.0536	$70.05	$70.05	$70.10
Purchase #4	$179.62	3.252%	$185.4612	$185.46	$185.45	$185.50
Purchase #5	$109.52	7.492%	$117.7252	$117.73	$117.75	$117.70
Purchase #6	$164.57	3.606%	$170.5044	$170.50	$170.50	$170.50
Purchase #7	$184.39	3.320%	$190.5117	$190.51	$190.50	$190.50
7 purchase totals =	$1,010.64		$1,058.8575	$1,058.86	$1,058.90	$1,058.90