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	$144.60	8.128%	$156.3531	$156.35	$156.35	$156.40
Purchase #2	$167.63	5.237%	$176.4088	$176.41	$176.40	$176.40
Purchase #3	$243.28	11.522%	$271.3107	$271.31	$271.30	$271.30
Purchase #4	$204.46	4.429%	$213.5155	$213.52	$213.50	$213.50
Purchase #5	$65.90	9.775%	$72.3417	$72.34	$72.35	$72.30
Purchase #6	$249.31	9.635%	$273.331	$273.33	$273.35	$273.30
Purchase #7	$102.36	8.640%	$111.2039	$111.20	$111.20	$111.20
7 purchase totals =	$1,177.54		$1,274.4647	$1,274.46	$1,274.45	$1,274.40