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	$100.34	13.600%	$113.9862	$113.99	$114.00	$114.00
Purchase #2	$115.72	9.750%	$127.0027	$127.00	$127.00	$127.00
Purchase #3	$5.40	13.129%	$6.109	$6.11	$6.10	$6.10
Purchase #4	$66.57	9.287%	$72.7524	$72.75	$72.75	$72.80
Purchase #5	$216.68	12.712%	$244.2244	$244.22	$244.20	$244.20
Purchase #6	$78.50	5.151%	$82.5435	$82.54	$82.55	$82.50
Purchase #7	$82.35	5.537%	$86.9097	$86.91	$86.90	$86.90
7 purchase totals =	$665.56		$733.5279	$733.52	$733.50	$733.50