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	$205.50	9.644%	$225.3184	$225.32	$225.30	$225.30
Purchase #2	$112.59	6.703%	$120.1369	$120.14	$120.15	$120.10
Purchase #3	$237.72	8.617%	$258.2043	$258.20	$258.20	$258.20
Purchase #4	$237.73	4.816%	$249.1791	$249.18	$249.20	$249.20
Purchase #5	$182.42	9.792%	$200.2826	$200.28	$200.30	$200.30
Purchase #6	$235.60	8.652%	$255.9841	$255.98	$256.00	$256.00
Purchase #7	$182.76	4.415%	$190.8289	$190.83	$190.85	$190.80
7 purchase totals =	$1,394.32		$1,499.9343	$1,499.93	$1,500.00	$1,499.90