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	$49.66	7.483%	$53.3761	$53.38	$53.40	$53.40
Purchase #2	$59.59	3.529%	$61.6929	$61.69	$61.70	$61.70
Purchase #3	$150.69	10.170%	$166.0152	$166.02	$166.00	$166.00
Purchase #4	$79.25	13.690%	$90.0993	$90.10	$90.10	$90.10
Purchase #5	$167.32	7.300%	$179.5344	$179.53	$179.55	$179.50
Purchase #6	$249.68	13.323%	$282.9449	$282.94	$282.95	$282.90
Purchase #7	$243.95	5.381%	$257.0769	$257.08	$257.10	$257.10
7 purchase totals =	$1,000.14		$1,090.7397	$1,090.74	$1,090.80	$1,090.70