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	$144.59	4.377%	$150.9187	$150.92	$150.90	$150.90
Purchase #2	$241.61	9.705%	$265.0583	$265.06	$265.05	$265.10
Purchase #3	$177.44	7.648%	$191.0106	$191.01	$191.00	$191.00
Purchase #4	$245.42	7.521%	$263.878	$263.88	$263.90	$263.90
Purchase #5	$121.29	13.352%	$137.4846	$137.48	$137.50	$137.50
Purchase #6	$215.61	9.711%	$236.5479	$236.55	$236.55	$236.50
Purchase #7	$223.38	13.347%	$253.1945	$253.19	$253.20	$253.20
7 purchase totals =	$1,369.34		$1,498.0926	$1,498.09	$1,498.10	$1,498.10