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	$44.29	3.392%	$45.7923	$45.79	$45.80	$45.80
Purchase #2	$241.89	12.782%	$272.8084	$272.81	$272.80	$272.80
Purchase #3	$52.93	11.533%	$59.0344	$59.03	$59.05	$59.00
Purchase #4	$228.95	3.172%	$236.2123	$236.21	$236.20	$236.20
Purchase #5	$85.75	4.450%	$89.5659	$89.57	$89.55	$89.60
Purchase #6	$85.63	10.718%	$94.8078	$94.81	$94.80	$94.80
Purchase #7	$233.36	5.279%	$245.6791	$245.68	$245.70	$245.70
7 purchase totals =	$972.80		$1,043.9002	$1,043.90	$1,043.90	$1,043.90