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	$39.88	4.130%	$41.527	$41.53	$41.55	$41.50
Purchase #2	$90.97	12.130%	$102.0047	$102.00	$102.00	$102.00
Purchase #3	$117.75	13.138%	$133.22	$133.22	$133.20	$133.20
Purchase #4	$51.34	4.223%	$53.5081	$53.51	$53.50	$53.50
Purchase #5	$243.72	8.484%	$264.3972	$264.40	$264.40	$264.40
Purchase #6	$102.43	13.687%	$116.4496	$116.45	$116.45	$116.40
Purchase #7	$105.71	7.332%	$113.4607	$113.46	$113.45	$113.50
7 purchase totals =	$751.80		$824.5673	$824.57	$824.55	$824.50