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	$188.33	6.144%	$199.901	$199.90	$199.90	$199.90
Purchase #2	$147.25	11.383%	$164.0115	$164.01	$164.00	$164.00
Purchase #3	$162.45	7.259%	$174.2422	$174.24	$174.25	$174.20
Purchase #4	$150.81	7.749%	$162.4963	$162.50	$162.50	$162.50
Purchase #5	$136.25	13.820%	$155.0798	$155.08	$155.10	$155.10
Purchase #6	$47.80	7.731%	$51.4954	$51.50	$51.50	$51.50
Purchase #7	$109.64	8.539%	$119.0022	$119.00	$119.00	$119.00
7 purchase totals =	$942.53		$1,026.2284	$1,026.23	$1,026.25	$1,026.20