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	$55.86	7.165%	$59.8624	$59.86	$59.85	$59.90
Purchase #2	$89.69	12.715%	$101.0941	$101.09	$101.10	$101.10
Purchase #3	$212.67	4.194%	$221.5894	$221.59	$221.60	$221.60
Purchase #4	$130.86	13.255%	$148.2055	$148.21	$148.20	$148.20
Purchase #5	$206.63	3.112%	$213.0603	$213.06	$213.05	$213.10
Purchase #6	$205.41	12.794%	$231.6902	$231.69	$231.70	$231.70
Purchase #7	$227.72	4.546%	$238.0722	$238.07	$238.05	$238.10
7 purchase totals =	$1,128.84		$1,213.5741	$1,213.57	$1,213.55	$1,213.70