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	$56.31	9.140%	$61.4567	$61.46	$61.45	$61.50
Purchase #2	$236.69	9.397%	$258.9318	$258.93	$258.95	$258.90
Purchase #3	$96.45	3.491%	$99.8171	$99.82	$99.80	$99.80
Purchase #4	$226.41	3.762%	$234.9275	$234.93	$234.95	$234.90
Purchase #5	$153.91	7.124%	$164.8745	$164.87	$164.85	$164.90
Purchase #6	$101.65	6.726%	$108.487	$108.49	$108.50	$108.50
Purchase #7	$50.88	9.488%	$55.7075	$55.71	$55.70	$55.70
7 purchase totals =	$922.30		$984.2021	$984.21	$984.20	$984.20