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	$234.34	4.284%	$244.3791	$244.38	$244.40	$244.40
Purchase #2	$40.73	4.688%	$42.6394	$42.64	$42.65	$42.60
Purchase #3	$129.48	3.833%	$134.443	$134.44	$134.45	$134.40
Purchase #4	$114.59	7.621%	$123.3229	$123.32	$123.30	$123.30
Purchase #5	$115.88	8.107%	$125.2744	$125.27	$125.25	$125.30
Purchase #6	$27.54	8.533%	$29.89	$29.89	$29.90	$29.90
Purchase #7	$80.90	5.722%	$85.5291	$85.53	$85.55	$85.50
7 purchase totals =	$743.46		$785.4779	$785.47	$785.50	$785.40