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	$204.57	6.705%	$218.2864	$218.29	$218.30	$218.30
Purchase #2	$53.71	10.597%	$59.4016	$59.40	$59.40	$59.40
Purchase #3	$13.43	6.835%	$14.3479	$14.35	$14.35	$14.30
Purchase #4	$73.65	11.392%	$82.0402	$82.04	$82.05	$82.00
Purchase #5	$51.40	12.550%	$57.8507	$57.85	$57.85	$57.90
Purchase #6	$244.38	8.530%	$265.2256	$265.23	$265.25	$265.20
Purchase #7	$219.84	12.849%	$248.0872	$248.09	$248.10	$248.10
7 purchase totals =	$860.98		$945.2396	$945.25	$945.30	$945.20