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	$141.83	9.796%	$155.7237	$155.72	$155.70	$155.70
Purchase #2	$89.85	4.576%	$93.9615	$93.96	$93.95	$94.00
Purchase #3	$89.25	11.666%	$99.6619	$99.66	$99.65	$99.70
Purchase #4	$206.61	7.874%	$222.8785	$222.88	$222.90	$222.90
Purchase #5	$196.40	10.807%	$217.6249	$217.62	$217.60	$217.60
Purchase #6	$210.39	11.347%	$234.263	$234.26	$234.25	$234.30
Purchase #7	$98.31	10.239%	$108.376	$108.38	$108.40	$108.40
7 purchase totals =	$1,032.64		$1,132.4895	$1,132.48	$1,132.45	$1,132.60