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	$60.25	5.587%	$63.6162	$63.62	$63.60	$63.60
Purchase #2	$139.72	12.652%	$157.3974	$157.40	$157.40	$157.40
Purchase #3	$71.71	9.358%	$78.4206	$78.42	$78.40	$78.40
Purchase #4	$89.98	5.244%	$94.6986	$94.70	$94.70	$94.70
Purchase #5	$197.27	13.244%	$223.3964	$223.40	$223.40	$223.40
Purchase #6	$105.27	5.666%	$111.2346	$111.23	$111.25	$111.20
Purchase #7	$168.76	12.376%	$189.6457	$189.65	$189.65	$189.60
7 purchase totals =	$832.96		$918.4095	$918.42	$918.40	$918.30