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	$99.60	10.159%	$109.7184	$109.72	$109.70	$109.70
Purchase #2	$106.92	6.166%	$113.5127	$113.51	$113.50	$113.50
Purchase #3	$111.50	5.673%	$117.8254	$117.83	$117.85	$117.80
Purchase #4	$242.86	10.228%	$267.6997	$267.70	$267.70	$267.70
Purchase #5	$129.91	12.668%	$146.367	$146.37	$146.35	$146.40
Purchase #6	$95.61	3.312%	$98.7766	$98.78	$98.80	$98.80
Purchase #7	$140.46	9.207%	$153.3922	$153.39	$153.40	$153.40
7 purchase totals =	$926.86		$1,007.2920	$1,007.30	$1,007.30	$1,007.30