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	$119.33	7.186%	$127.9051	$127.91	$127.90	$127.90
Purchase #2	$28.82	13.781%	$32.7917	$32.79	$32.80	$32.80
Purchase #3	$236.93	9.152%	$258.6138	$258.61	$258.60	$258.60
Purchase #4	$113.54	9.254%	$124.047	$124.05	$124.05	$124.00
Purchase #5	$108.41	9.560%	$118.774	$118.77	$118.75	$118.80
Purchase #6	$226.43	5.513%	$238.9131	$238.91	$238.90	$238.90
Purchase #7	$34.43	3.477%	$35.6271	$35.63	$35.65	$35.60
7 purchase totals =	$867.89		$936.6718	$936.67	$936.65	$936.60