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	$248.64	10.421%	$274.5508	$274.55	$274.55	$274.60
Purchase #2	$147.46	3.473%	$152.5813	$152.58	$152.60	$152.60
Purchase #3	$116.54	5.751%	$123.2422	$123.24	$123.25	$123.20
Purchase #4	$192.44	6.434%	$204.8216	$204.82	$204.80	$204.80
Purchase #5	$215.25	3.412%	$222.5943	$222.59	$222.60	$222.60
Purchase #6	$36.75	13.613%	$41.7528	$41.75	$41.75	$41.80
Purchase #7	$91.90	11.641%	$102.5981	$102.60	$102.60	$102.60
7 purchase totals =	$1,048.98		$1,122.1411	$1,122.13	$1,122.15	$1,122.20