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	$147.45	4.844%	$154.5925	$154.59	$154.60	$154.60
Purchase #2	$88.36	6.553%	$94.1502	$94.15	$94.15	$94.20
Purchase #3	$68.94	11.182%	$76.6489	$76.65	$76.65	$76.60
Purchase #4	$250.85	7.540%	$269.7641	$269.76	$269.75	$269.80
Purchase #5	$31.46	6.788%	$33.5955	$33.60	$33.60	$33.60
Purchase #6	$155.89	4.242%	$162.5029	$162.50	$162.50	$162.50
Purchase #7	$184.58	11.195%	$205.2437	$205.24	$205.25	$205.20
7 purchase totals =	$927.53		$996.4978	$996.49	$996.50	$996.50