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	$96.76	8.680%	$105.1588	$105.16	$105.15	$105.20
Purchase #2	$87.89	9.697%	$96.4127	$96.41	$96.40	$96.40
Purchase #3	$123.89	6.277%	$131.6666	$131.67	$131.65	$131.70
Purchase #4	$148.31	5.368%	$156.2713	$156.27	$156.25	$156.30
Purchase #5	$241.27	8.269%	$261.2206	$261.22	$261.20	$261.20
Purchase #6	$166.86	9.700%	$183.0454	$183.05	$183.05	$183.00
Purchase #7	$229.70	7.379%	$246.6496	$246.65	$246.65	$246.60
7 purchase totals =	$1,094.68		$1,180.4250	$1,180.43	$1,180.35	$1,180.40