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	$78.25	11.260%	$87.061	$87.06	$87.05	$87.10
Purchase #2	$124.63	13.715%	$141.723	$141.72	$141.70	$141.70
Purchase #3	$39.95	11.524%	$44.5538	$44.55	$44.55	$44.60
Purchase #4	$115.67	11.365%	$128.8159	$128.82	$128.80	$128.80
Purchase #5	$229.41	3.847%	$238.2354	$238.24	$238.25	$238.20
Purchase #6	$184.90	6.512%	$196.9407	$196.94	$196.95	$196.90
Purchase #7	$238.98	8.853%	$260.1369	$260.14	$260.15	$260.10
7 purchase totals =	$1,011.79		$1,097.4667	$1,097.47	$1,097.45	$1,097.40