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	$48.54	13.765%	$55.2215	$55.22	$55.20	$55.20
Purchase #2	$195.77	11.156%	$217.6101	$217.61	$217.60	$217.60
Purchase #3	$175.32	13.266%	$198.578	$198.58	$198.60	$198.60
Purchase #4	$123.36	6.314%	$131.149	$131.15	$131.15	$131.10
Purchase #5	$73.63	11.208%	$81.8825	$81.88	$81.90	$81.90
Purchase #6	$96.33	4.657%	$100.8161	$100.82	$100.80	$100.80
Purchase #7	$180.28	8.643%	$195.8616	$195.86	$195.85	$195.90
7 purchase totals =	$893.23		$981.1188	$981.12	$981.10	$981.10