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	$92.63	7.538%	$99.6124	$99.61	$99.60	$99.60
Purchase #2	$21.98	10.409%	$24.2679	$24.27	$24.25	$24.30
Purchase #3	$112.95	12.155%	$126.6791	$126.68	$126.70	$126.70
Purchase #4	$25.71	6.825%	$27.4647	$27.46	$27.45	$27.50
Purchase #5	$115.59	3.413%	$119.5351	$119.54	$119.55	$119.50
Purchase #6	$118.96	10.575%	$131.54	$131.54	$131.55	$131.50
Purchase #7	$200.30	3.251%	$206.8118	$206.81	$206.80	$206.80
7 purchase totals =	$688.12		$735.9110	$735.91	$735.90	$735.90