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	$206.79	7.450%	$222.1959	$222.20	$222.20	$222.20
Purchase #2	$5.64	8.542%	$6.1218	$6.12	$6.10	$6.10
Purchase #3	$105.35	6.624%	$112.3284	$112.33	$112.35	$112.30
Purchase #4	$172.62	7.689%	$185.8928	$185.89	$185.90	$185.90
Purchase #5	$161.52	9.527%	$176.908	$176.91	$176.90	$176.90
Purchase #6	$31.32	3.705%	$32.4804	$32.48	$32.50	$32.50
Purchase #7	$63.39	11.848%	$70.9004	$70.90	$70.90	$70.90
7 purchase totals =	$746.63		$806.8277	$806.83	$806.85	$806.80