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	$131.37	10.784%	$145.5369	$145.54	$145.55	$145.50
Purchase #2	$82.39	3.478%	$85.2555	$85.26	$85.25	$85.30
Purchase #3	$143.92	3.393%	$148.8032	$148.80	$148.80	$148.80
Purchase #4	$36.63	9.810%	$40.2234	$40.22	$40.20	$40.20
Purchase #5	$11.66	13.810%	$13.2702	$13.27	$13.25	$13.30
Purchase #6	$190.39	5.571%	$200.9966	$201.00	$201.00	$201.00
Purchase #7	$102.28	11.718%	$114.2652	$114.27	$114.25	$114.30
7 purchase totals =	$698.64		$748.3510	$748.36	$748.30	$748.40