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	$131.91	8.348%	$142.9218	$142.92	$142.90	$142.90
Purchase #2	$203.47	3.540%	$210.6728	$210.67	$210.65	$210.70
Purchase #3	$217.47	9.771%	$238.719	$238.72	$238.70	$238.70
Purchase #4	$116.47	10.165%	$128.3092	$128.31	$128.30	$128.30
Purchase #5	$157.89	8.611%	$171.4859	$171.49	$171.50	$171.50
Purchase #6	$240.95	12.597%	$271.3025	$271.30	$271.30	$271.30
Purchase #7	$210.51	12.814%	$237.4848	$237.48	$237.50	$237.50
7 purchase totals =	$1,278.67		$1,400.8960	$1,400.89	$1,400.85	$1,400.90