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	$154.99	3.573%	$160.5278	$160.53	$160.55	$160.50
Purchase #2	$94.53	5.290%	$99.5306	$99.53	$99.55	$99.50
Purchase #3	$236.40	11.436%	$263.4347	$263.43	$263.45	$263.40
Purchase #4	$213.94	5.369%	$225.4264	$225.43	$225.45	$225.40
Purchase #5	$57.67	6.289%	$61.2969	$61.30	$61.30	$61.30
Purchase #6	$169.89	4.220%	$177.0594	$177.06	$177.05	$177.10
Purchase #7	$13.76	9.455%	$15.061	$15.06	$15.05	$15.10
7 purchase totals =	$941.18		$1,002.3368	$1,002.34	$1,002.40	$1,002.30