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	$181.87	10.258%	$200.5262	$200.53	$200.55	$200.50
Purchase #2	$124.78	13.328%	$141.4107	$141.41	$141.40	$141.40
Purchase #3	$64.70	9.860%	$71.0794	$71.08	$71.10	$71.10
Purchase #4	$146.98	6.195%	$156.0854	$156.09	$156.10	$156.10
Purchase #5	$63.33	13.777%	$72.055	$72.06	$72.05	$72.10
Purchase #6	$148.53	9.853%	$163.1647	$163.16	$163.15	$163.20
Purchase #7	$158.37	7.637%	$170.4647	$170.46	$170.45	$170.50
7 purchase totals =	$888.56		$974.7861	$974.79	$974.80	$974.90