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	$97.29	12.430%	$109.3831	$109.38	$109.40	$109.40
Purchase #2	$171.76	4.598%	$179.6575	$179.66	$179.65	$179.70
Purchase #3	$49.74	6.155%	$52.8015	$52.80	$52.80	$52.80
Purchase #4	$192.84	6.581%	$205.5308	$205.53	$205.55	$205.50
Purchase #5	$183.46	10.347%	$202.4426	$202.44	$202.45	$202.40
Purchase #6	$85.85	5.152%	$90.273	$90.27	$90.25	$90.30
Purchase #7	$248.35	9.325%	$271.5086	$271.51	$271.50	$271.50
7 purchase totals =	$1,029.29		$1,111.5971	$1,111.59	$1,111.60	$1,111.60