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	$181.35	10.154%	$199.7643	$199.76	$199.75	$199.80
Purchase #2	$38.71	5.616%	$40.884	$40.88	$40.90	$40.90
Purchase #3	$93.87	9.515%	$102.8017	$102.80	$102.80	$102.80
Purchase #4	$49.98	10.603%	$55.2794	$55.28	$55.30	$55.30
Purchase #5	$19.89	5.108%	$20.906	$20.91	$20.90	$20.90
Purchase #6	$48.35	3.166%	$49.8808	$49.88	$49.90	$49.90
Purchase #7	$41.53	9.280%	$45.384	$45.38	$45.40	$45.40
7 purchase totals =	$473.68		$514.9002	$514.89	$514.95	$515.00