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	$117.69	11.490%	$131.2126	$131.21	$131.20	$131.20
Purchase #2	$130.27	5.560%	$137.513	$137.51	$137.50	$137.50
Purchase #3	$228.99	7.347%	$245.8139	$245.81	$245.80	$245.80
Purchase #4	$69.38	13.385%	$78.6665	$78.67	$78.65	$78.70
Purchase #5	$40.99	6.665%	$43.722	$43.72	$43.70	$43.70
Purchase #6	$142.79	13.741%	$162.4108	$162.41	$162.40	$162.40
Purchase #7	$63.50	13.381%	$71.9969	$72.00	$72.00	$72.00
7 purchase totals =	$793.61		$871.3357	$871.33	$871.25	$871.30