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	$140.69	6.788%	$150.24	$150.24	$150.25	$150.20
Purchase #2	$149.80	3.513%	$155.0625	$155.06	$155.05	$155.10
Purchase #3	$174.86	9.824%	$192.0382	$192.04	$192.05	$192.00
Purchase #4	$85.84	11.235%	$95.4841	$95.48	$95.50	$95.50
Purchase #5	$37.40	7.747%	$40.2974	$40.30	$40.30	$40.30
Purchase #6	$182.32	7.432%	$195.87	$195.87	$195.85	$195.90
Purchase #7	$173.95	10.153%	$191.6111	$191.61	$191.60	$191.60
7 purchase totals =	$944.86		$1,020.6033	$1,020.60	$1,020.60	$1,020.60