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	$111.51	4.848%	$116.916	$116.92	$116.90	$116.90
Purchase #2	$38.52	10.131%	$42.4225	$42.42	$42.40	$42.40
Purchase #3	$241.36	4.386%	$251.946	$251.95	$251.95	$251.90
Purchase #4	$142.30	3.644%	$147.4854	$147.49	$147.50	$147.50
Purchase #5	$150.35	4.124%	$156.5504	$156.55	$156.55	$156.60
Purchase #6	$54.84	3.463%	$56.7391	$56.74	$56.75	$56.70
Purchase #7	$20.69	7.656%	$22.274	$22.27	$22.25	$22.30
7 purchase totals =	$759.57		$794.3334	$794.34	$794.30	$794.30