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	$138.49	7.478%	$148.8463	$148.85	$148.85	$148.80
Purchase #2	$211.27	12.715%	$238.133	$238.13	$238.15	$238.10
Purchase #3	$213.26	9.364%	$233.2297	$233.23	$233.25	$233.20
Purchase #4	$45.70	13.307%	$51.7813	$51.78	$51.80	$51.80
Purchase #5	$134.28	13.566%	$152.4964	$152.50	$152.50	$152.50
Purchase #6	$101.95	12.779%	$114.9782	$114.98	$115.00	$115.00
Purchase #7	$188.58	6.528%	$200.8905	$200.89	$200.90	$200.90
7 purchase totals =	$1,033.53		$1,140.3554	$1,140.36	$1,140.45	$1,140.30