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	$233.26	4.817%	$244.4961	$244.50	$244.50	$244.50
Purchase #2	$123.45	12.780%	$139.2269	$139.23	$139.25	$139.20
Purchase #3	$136.43	10.613%	$150.9093	$150.91	$150.90	$150.90
Purchase #4	$158.40	8.248%	$171.4648	$171.46	$171.45	$171.50
Purchase #5	$31.63	4.855%	$33.1656	$33.17	$33.15	$33.20
Purchase #6	$198.37	13.288%	$224.7294	$224.73	$224.75	$224.70
Purchase #7	$192.41	13.467%	$218.3219	$218.32	$218.30	$218.30
7 purchase totals =	$1,073.95		$1,182.3140	$1,182.32	$1,182.30	$1,182.30