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	$40.64	9.526%	$44.5114	$44.51	$44.50	$44.50
Purchase #2	$223.28	4.439%	$233.1914	$233.19	$233.20	$233.20
Purchase #3	$86.80	4.336%	$90.5636	$90.56	$90.55	$90.60
Purchase #4	$48.53	12.312%	$54.505	$54.51	$54.50	$54.50
Purchase #5	$139.78	13.438%	$158.5636	$158.56	$158.55	$158.60
Purchase #6	$188.89	3.764%	$195.9998	$196.00	$196.00	$196.00
Purchase #7	$72.38	3.747%	$75.0921	$75.09	$75.10	$75.10
7 purchase totals =	$800.30		$852.4269	$852.42	$852.40	$852.50