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	$44.61	6.267%	$47.4057	$47.41	$47.40	$47.40
Purchase #2	$125.36	4.797%	$131.3735	$131.37	$131.35	$131.40
Purchase #3	$205.52	13.759%	$233.7975	$233.80	$233.80	$233.80
Purchase #4	$225.98	10.869%	$250.5418	$250.54	$250.55	$250.50
Purchase #5	$180.48	8.685%	$196.1547	$196.15	$196.15	$196.20
Purchase #6	$33.95	4.381%	$35.4373	$35.44	$35.45	$35.40
Purchase #7	$117.83	7.318%	$126.4528	$126.45	$126.45	$126.50
7 purchase totals =	$933.73		$1,021.1633	$1,021.16	$1,021.15	$1,021.20