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	$201.65	9.330%	$220.4639	$220.46	$220.45	$220.50
Purchase #2	$236.47	13.340%	$268.0151	$268.02	$268.00	$268.00
Purchase #3	$137.78	3.553%	$142.6753	$142.68	$142.70	$142.70
Purchase #4	$151.40	10.581%	$167.4196	$167.42	$167.40	$167.40
Purchase #5	$78.29	4.637%	$81.9203	$81.92	$81.90	$81.90
Purchase #6	$106.89	3.765%	$110.9144	$110.91	$110.90	$110.90
Purchase #7	$82.61	8.693%	$89.7913	$89.79	$89.80	$89.80
7 purchase totals =	$995.09		$1,081.1999	$1,081.20	$1,081.15	$1,081.20