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	$198.64	4.720%	$208.0158	$208.02	$208.00	$208.00
Purchase #2	$82.25	11.667%	$91.8461	$91.85	$91.85	$91.80
Purchase #3	$243.52	12.720%	$274.4957	$274.50	$274.50	$274.50
Purchase #4	$181.76	7.193%	$194.834	$194.83	$194.85	$194.80
Purchase #5	$162.35	3.613%	$168.2157	$168.22	$168.20	$168.20
Purchase #6	$186.34	11.789%	$208.3076	$208.31	$208.30	$208.30
Purchase #7	$65.82	11.315%	$73.2675	$73.27	$73.25	$73.30
7 purchase totals =	$1,120.68		$1,218.9824	$1,219.00	$1,218.95	$1,218.90