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	$15.28	4.301%	$15.9372	$15.94	$15.95	$15.90
Purchase #2	$250.35	3.200%	$258.3612	$258.36	$258.35	$258.40
Purchase #3	$50.73	10.553%	$56.0835	$56.08	$56.10	$56.10
Purchase #4	$84.82	3.145%	$87.4876	$87.49	$87.50	$87.50
Purchase #5	$243.98	5.157%	$256.562	$256.56	$256.55	$256.60
Purchase #6	$188.33	4.188%	$196.2173	$196.22	$196.20	$196.20
Purchase #7	$48.59	12.759%	$54.7896	$54.79	$54.80	$54.80
7 purchase totals =	$882.08		$925.4384	$925.44	$925.45	$925.50