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	$47.42	12.671%	$53.4286	$53.43	$53.45	$53.40
Purchase #2	$250.37	5.371%	$263.8174	$263.82	$263.80	$263.80
Purchase #3	$38.82	3.338%	$40.1158	$40.12	$40.10	$40.10
Purchase #4	$79.93	7.456%	$85.8896	$85.89	$85.90	$85.90
Purchase #5	$236.33	11.473%	$263.4441	$263.44	$263.45	$263.40
Purchase #6	$180.33	6.499%	$192.0496	$192.05	$192.05	$192.00
Purchase #7	$137.53	5.847%	$145.5714	$145.57	$145.55	$145.60
7 purchase totals =	$970.73		$1,044.3165	$1,044.32	$1,044.30	$1,044.20