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	$178.50	8.309%	$193.3316	$193.33	$193.35	$193.30
Purchase #2	$134.69	4.698%	$141.0177	$141.02	$141.00	$141.00
Purchase #3	$157.68	9.357%	$172.4341	$172.43	$172.45	$172.40
Purchase #4	$158.29	12.709%	$178.4071	$178.41	$178.40	$178.40
Purchase #5	$91.85	3.503%	$95.0675	$95.07	$95.05	$95.10
Purchase #6	$90.60	8.428%	$98.2358	$98.24	$98.25	$98.20
Purchase #7	$133.50	5.473%	$140.8065	$140.81	$140.80	$140.80
7 purchase totals =	$945.11		$1,019.3003	$1,019.31	$1,019.30	$1,019.20