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	$97.57	12.110%	$109.3857	$109.39	$109.40	$109.40
Purchase #2	$64.42	6.471%	$68.5886	$68.59	$68.60	$68.60
Purchase #3	$142.44	6.826%	$152.163	$152.16	$152.15	$152.20
Purchase #4	$91.47	8.347%	$99.105	$99.11	$99.10	$99.10
Purchase #5	$38.88	9.294%	$42.4935	$42.49	$42.50	$42.50
Purchase #6	$197.37	5.423%	$208.0734	$208.07	$208.05	$208.10
Purchase #7	$189.92	3.691%	$196.9299	$196.93	$196.95	$196.90
7 purchase totals =	$822.07		$876.7391	$876.74	$876.75	$876.80