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	$221.48	8.555%	$240.4276	$240.43	$240.45	$240.40
Purchase #2	$154.79	9.360%	$169.2783	$169.28	$169.30	$169.30
Purchase #3	$64.84	3.172%	$66.8967	$66.90	$66.90	$66.90
Purchase #4	$99.33	9.790%	$109.0544	$109.05	$109.05	$109.10
Purchase #5	$103.49	7.267%	$111.0106	$111.01	$111.00	$111.00
Purchase #6	$124.73	3.309%	$128.8573	$128.86	$128.85	$128.90
Purchase #7	$69.94	9.847%	$76.827	$76.83	$76.85	$76.80
7 purchase totals =	$838.60		$902.3519	$902.36	$902.40	$902.40