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	$81.43	10.440%	$89.9313	$89.93	$89.95	$89.90
Purchase #2	$64.33	12.568%	$72.415	$72.42	$72.40	$72.40
Purchase #3	$127.72	13.546%	$145.021	$145.02	$145.00	$145.00
Purchase #4	$156.67	5.184%	$164.7918	$164.79	$164.80	$164.80
Purchase #5	$247.79	13.328%	$280.8155	$280.82	$280.80	$280.80
Purchase #6	$15.53	13.598%	$17.6418	$17.64	$17.65	$17.60
Purchase #7	$46.81	12.352%	$52.592	$52.59	$52.60	$52.60
7 purchase totals =	$740.28		$823.2084	$823.21	$823.20	$823.10