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	$200.54	9.394%	$219.3787	$219.38	$219.40	$219.40
Purchase #2	$186.33	7.465%	$200.2395	$200.24	$200.25	$200.20
Purchase #3	$220.53	4.505%	$230.4649	$230.46	$230.45	$230.50
Purchase #4	$212.75	5.111%	$223.6237	$223.62	$223.60	$223.60
Purchase #5	$156.29	7.477%	$167.9758	$167.98	$168.00	$168.00
Purchase #6	$118.82	4.720%	$124.4283	$124.43	$124.45	$124.40
Purchase #7	$33.60	3.205%	$34.6769	$34.68	$34.70	$34.70
7 purchase totals =	$1,128.86		$1,200.7878	$1,200.79	$1,200.85	$1,200.80