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	$217.82	9.339%	$238.1622	$238.16	$238.15	$238.20
Purchase #2	$224.69	5.414%	$236.8547	$236.85	$236.85	$236.90
Purchase #3	$5.70	3.299%	$5.888	$5.89	$5.90	$5.90
Purchase #4	$59.57	3.658%	$61.7491	$61.75	$61.75	$61.70
Purchase #5	$21.98	8.385%	$23.823	$23.82	$23.80	$23.80
Purchase #6	$74.36	9.663%	$81.5454	$81.55	$81.55	$81.50
Purchase #7	$85.29	4.624%	$89.2338	$89.23	$89.25	$89.20
7 purchase totals =	$689.41		$737.2562	$737.25	$737.25	$737.20