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	$194.38	11.582%	$216.8931	$216.89	$216.90	$216.90
Purchase #2	$99.77	10.504%	$110.2498	$110.25	$110.25	$110.20
Purchase #3	$76.51	12.299%	$85.92	$85.92	$85.90	$85.90
Purchase #4	$117.67	5.537%	$124.1854	$124.19	$124.20	$124.20
Purchase #5	$164.29	9.318%	$179.5985	$179.60	$179.60	$179.60
Purchase #6	$168.37	9.871%	$184.9898	$184.99	$185.00	$185.00
Purchase #7	$137.86	13.489%	$156.4559	$156.46	$156.45	$156.50
7 purchase totals =	$958.85		$1,058.2925	$1,058.30	$1,058.30	$1,058.30