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	$89.79	5.843%	$95.0364	$95.04	$95.05	$95.00
Purchase #2	$39.94	7.110%	$42.7797	$42.78	$42.80	$42.80
Purchase #3	$246.34	13.762%	$280.2413	$280.24	$280.25	$280.20
Purchase #4	$132.40	6.119%	$140.5016	$140.50	$140.50	$140.50
Purchase #5	$133.43	6.111%	$141.5839	$141.58	$141.60	$141.60
Purchase #6	$202.86	4.558%	$212.1064	$212.11	$212.10	$212.10
Purchase #7	$206.50	5.850%	$218.5803	$218.58	$218.60	$218.60
7 purchase totals =	$1,051.26		$1,130.8296	$1,130.83	$1,130.90	$1,130.80