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	$164.27	4.415%	$171.5225	$171.52	$171.50	$171.50
Purchase #2	$190.41	3.277%	$196.6497	$196.65	$196.65	$196.60
Purchase #3	$189.38	3.792%	$196.5613	$196.56	$196.55	$196.60
Purchase #4	$109.68	6.787%	$117.124	$117.12	$117.10	$117.10
Purchase #5	$94.72	9.842%	$104.0423	$104.04	$104.05	$104.00
Purchase #6	$147.52	9.747%	$161.8988	$161.90	$161.90	$161.90
Purchase #7	$97.83	13.680%	$111.2131	$111.21	$111.20	$111.20
7 purchase totals =	$993.81		$1,059.0117	$1,059.00	$1,058.95	$1,058.90