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	$191.49	11.592%	$213.6875	$213.69	$213.70	$213.70
Purchase #2	$175.52	7.463%	$188.6191	$188.62	$188.60	$188.60
Purchase #3	$144.56	8.684%	$157.1136	$157.11	$157.10	$157.10
Purchase #4	$202.81	6.155%	$215.293	$215.29	$215.30	$215.30
Purchase #5	$121.48	8.267%	$131.5228	$131.52	$131.50	$131.50
Purchase #6	$111.56	11.434%	$124.3158	$124.32	$124.30	$124.30
Purchase #7	$133.46	5.692%	$141.0565	$141.06	$141.05	$141.10
7 purchase totals =	$1,080.88		$1,171.6083	$1,171.61	$1,171.55	$1,171.60