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	$155.79	11.417%	$173.5765	$173.58	$173.60	$173.60
Purchase #2	$101.31	11.494%	$112.9546	$112.95	$112.95	$113.00
Purchase #3	$212.50	13.673%	$241.5551	$241.56	$241.55	$241.60
Purchase #4	$90.95	5.665%	$96.1023	$96.10	$96.10	$96.10
Purchase #5	$158.40	4.644%	$165.7561	$165.76	$165.75	$165.80
Purchase #6	$236.25	12.860%	$266.6318	$266.63	$266.65	$266.60
Purchase #7	$37.94	4.351%	$39.5908	$39.59	$39.60	$39.60
7 purchase totals =	$993.14		$1,096.1672	$1,096.17	$1,096.20	$1,096.30