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	$89.27	11.258%	$99.32	$99.32	$99.30	$99.30
Purchase #2	$57.45	12.644%	$64.714	$64.71	$64.70	$64.70
Purchase #3	$17.46	6.262%	$18.5533	$18.55	$18.55	$18.60
Purchase #4	$212.45	5.592%	$224.3302	$224.33	$224.35	$224.30
Purchase #5	$201.91	4.238%	$210.4669	$210.47	$210.45	$210.50
Purchase #6	$140.86	12.379%	$158.2971	$158.30	$158.30	$158.30
Purchase #7	$69.98	8.703%	$76.0704	$76.07	$76.05	$76.10
7 purchase totals =	$789.38		$851.7519	$851.75	$851.70	$851.80