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	$198.45	7.242%	$212.8217	$212.82	$212.80	$212.80
Purchase #2	$163.92	3.479%	$169.6228	$169.62	$169.60	$169.60
Purchase #3	$160.75	8.316%	$174.118	$174.12	$174.10	$174.10
Purchase #4	$160.89	4.806%	$168.6224	$168.62	$168.60	$168.60
Purchase #5	$169.75	7.533%	$182.5373	$182.54	$182.55	$182.50
Purchase #6	$111.32	5.431%	$117.3658	$117.37	$117.35	$117.40
Purchase #7	$56.76	4.102%	$59.0883	$59.09	$59.10	$59.10
7 purchase totals =	$1,021.84		$1,084.1763	$1,084.18	$1,084.10	$1,084.10