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	$41.51	13.590%	$47.1512	$47.15	$47.15	$47.20
Purchase #2	$105.53	5.525%	$111.3605	$111.36	$111.35	$111.40
Purchase #3	$202.94	4.402%	$211.8734	$211.87	$211.85	$211.90
Purchase #4	$123.98	12.755%	$139.7936	$139.79	$139.80	$139.80
Purchase #5	$184.47	12.282%	$207.1266	$207.13	$207.15	$207.10
Purchase #6	$19.78	9.264%	$21.6124	$21.61	$21.60	$21.60
Purchase #7	$80.61	5.619%	$85.1395	$85.14	$85.15	$85.10
7 purchase totals =	$758.82		$824.0572	$824.05	$824.05	$824.10