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	$142.86	8.332%	$154.7631	$154.76	$154.75	$154.80
Purchase #2	$142.32	5.697%	$150.428	$150.43	$150.45	$150.40
Purchase #3	$217.40	3.189%	$224.3329	$224.33	$224.35	$224.30
Purchase #4	$211.64	8.276%	$229.1553	$229.16	$229.15	$229.20
Purchase #5	$103.89	5.739%	$109.8522	$109.85	$109.85	$109.90
Purchase #6	$42.41	11.547%	$47.3071	$47.31	$47.30	$47.30
Purchase #7	$40.56	13.163%	$45.8989	$45.90	$45.90	$45.90
7 purchase totals =	$901.08		$961.7375	$961.74	$961.75	$961.80