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	$20.29	13.120%	$22.952	$22.95	$22.95	$23.00
Purchase #2	$38.77	7.155%	$41.544	$41.54	$41.55	$41.50
Purchase #3	$77.59	6.804%	$82.8692	$82.87	$82.85	$82.90
Purchase #4	$65.52	5.215%	$68.9369	$68.94	$68.95	$68.90
Purchase #5	$81.31	13.620%	$92.3844	$92.38	$92.40	$92.40
Purchase #6	$63.95	4.139%	$66.5969	$66.60	$66.60	$66.60
Purchase #7	$43.88	3.352%	$45.3509	$45.35	$45.35	$45.40
7 purchase totals =	$391.31		$420.6343	$420.63	$420.65	$420.70