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	$118.49	7.321%	$127.1647	$127.16	$127.15	$127.20
Purchase #2	$29.45	9.221%	$32.1656	$32.17	$32.15	$32.20
Purchase #3	$106.46	6.701%	$113.5939	$113.59	$113.60	$113.60
Purchase #4	$72.68	7.855%	$78.389	$78.39	$78.40	$78.40
Purchase #5	$181.33	13.645%	$206.0725	$206.07	$206.05	$206.10
Purchase #6	$187.85	4.368%	$196.0553	$196.06	$196.05	$196.10
Purchase #7	$212.68	13.861%	$242.1596	$242.16	$242.15	$242.20
7 purchase totals =	$908.94		$995.6006	$995.60	$995.55	$995.80