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	$197.82	10.682%	$218.9511	$218.95	$218.95	$219.00
Purchase #2	$171.88	5.486%	$181.3093	$181.31	$181.30	$181.30
Purchase #3	$51.81	6.725%	$55.2942	$55.29	$55.30	$55.30
Purchase #4	$41.34	4.171%	$43.0643	$43.06	$43.05	$43.10
Purchase #5	$90.59	5.254%	$95.3496	$95.35	$95.35	$95.30
Purchase #6	$53.86	12.714%	$60.7078	$60.71	$60.70	$60.70
Purchase #7	$151.53	9.209%	$165.4844	$165.48	$165.50	$165.50
7 purchase totals =	$758.83		$820.1607	$820.15	$820.15	$820.20