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	$117.34	5.325%	$123.5884	$123.59	$123.60	$123.60
Purchase #2	$153.88	6.741%	$164.2531	$164.25	$164.25	$164.30
Purchase #3	$229.47	8.270%	$248.4472	$248.45	$248.45	$248.40
Purchase #4	$180.51	6.765%	$192.7215	$192.72	$192.70	$192.70
Purchase #5	$159.73	4.324%	$166.6367	$166.64	$166.65	$166.60
Purchase #6	$59.47	7.428%	$63.8874	$63.89	$63.90	$63.90
Purchase #7	$52.95	12.787%	$59.7207	$59.72	$59.70	$59.70
7 purchase totals =	$953.35		$1,019.2550	$1,019.26	$1,019.25	$1,019.20