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	$118.34	3.840%	$122.8843	$122.88	$122.90	$122.90
Purchase #2	$125.33	4.822%	$131.3734	$131.37	$131.35	$131.40
Purchase #3	$228.42	13.471%	$259.1905	$259.19	$259.20	$259.20
Purchase #4	$41.96	9.253%	$45.8426	$45.84	$45.85	$45.80
Purchase #5	$180.71	8.650%	$196.3414	$196.34	$196.35	$196.30
Purchase #6	$173.59	11.457%	$193.4782	$193.48	$193.50	$193.50
Purchase #7	$49.94	10.751%	$55.309	$55.31	$55.30	$55.30
7 purchase totals =	$918.29		$1,004.4194	$1,004.41	$1,004.45	$1,004.40