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	$49.28	9.645%	$54.0331	$54.03	$54.05	$54.00
Purchase #2	$196.28	12.148%	$220.1241	$220.12	$220.10	$220.10
Purchase #3	$50.77	6.315%	$53.9761	$53.98	$54.00	$54.00
Purchase #4	$102.31	8.817%	$111.3307	$111.33	$111.35	$111.30
Purchase #5	$239.37	5.204%	$251.8268	$251.83	$251.85	$251.80
Purchase #6	$203.81	3.464%	$210.87	$210.87	$210.85	$210.90
Purchase #7	$227.40	9.161%	$248.2321	$248.23	$248.25	$248.20
7 purchase totals =	$1,069.22		$1,150.3929	$1,150.39	$1,150.45	$1,150.30