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	$145.34	5.168%	$152.8512	$152.85	$152.85	$152.90
Purchase #2	$205.88	12.192%	$230.9809	$230.98	$231.00	$231.00
Purchase #3	$231.82	8.172%	$250.7643	$250.76	$250.75	$250.80
Purchase #4	$233.50	13.841%	$265.8187	$265.82	$265.80	$265.80
Purchase #5	$25.87	7.849%	$27.9005	$27.90	$27.90	$27.90
Purchase #6	$102.38	10.551%	$113.1821	$113.18	$113.20	$113.20
Purchase #7	$204.45	8.753%	$222.3455	$222.35	$222.35	$222.30
7 purchase totals =	$1,149.24		$1,263.8432	$1,263.84	$1,263.85	$1,263.90