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	$221.45	5.553%	$233.7471	$233.75	$233.75	$233.70
Purchase #2	$43.70	3.800%	$45.3606	$45.36	$45.35	$45.40
Purchase #3	$197.88	13.604%	$224.7996	$224.80	$224.80	$224.80
Purchase #4	$54.54	6.663%	$58.174	$58.17	$58.15	$58.20
Purchase #5	$215.81	9.578%	$236.4803	$236.48	$236.50	$236.50
Purchase #6	$211.98	12.704%	$238.9099	$238.91	$238.90	$238.90
Purchase #7	$122.44	7.356%	$131.4467	$131.45	$131.45	$131.40
7 purchase totals =	$1,067.80		$1,168.9182	$1,168.92	$1,168.90	$1,168.90