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	$109.29	6.263%	$116.1348	$116.13	$116.15	$116.10
Purchase #2	$154.27	7.541%	$165.9035	$165.90	$165.90	$165.90
Purchase #3	$34.73	7.798%	$37.4382	$37.44	$37.45	$37.40
Purchase #4	$82.37	10.439%	$90.9686	$90.97	$90.95	$91.00
Purchase #5	$43.66	9.402%	$47.7649	$47.76	$47.75	$47.80
Purchase #6	$43.57	7.563%	$46.8652	$46.87	$46.85	$46.90
Purchase #7	$214.67	4.758%	$224.884	$224.88	$224.90	$224.90
7 purchase totals =	$682.56		$729.9592	$729.95	$729.95	$730.00