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	$63.75	11.850%	$71.3044	$71.30	$71.30	$71.30
Purchase #2	$237.52	3.697%	$246.3011	$246.30	$246.30	$246.30
Purchase #3	$24.56	11.681%	$27.4289	$27.43	$27.45	$27.40
Purchase #4	$214.57	3.200%	$221.4362	$221.44	$221.45	$221.40
Purchase #5	$62.51	13.847%	$71.1658	$71.17	$71.15	$71.20
Purchase #6	$136.47	6.443%	$145.2628	$145.26	$145.25	$145.30
Purchase #7	$196.79	12.315%	$221.0247	$221.02	$221.00	$221.00
7 purchase totals =	$936.17		$1,003.9239	$1,003.92	$1,003.90	$1,003.90