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	$40.70	10.715%	$45.061	$45.06	$45.05	$45.10
Purchase #2	$52.30	9.142%	$57.0813	$57.08	$57.10	$57.10
Purchase #3	$194.52	3.253%	$200.8477	$200.85	$200.85	$200.80
Purchase #4	$26.67	10.431%	$29.4519	$29.45	$29.45	$29.50
Purchase #5	$119.83	11.423%	$133.5182	$133.52	$133.50	$133.50
Purchase #6	$20.95	11.239%	$23.3046	$23.30	$23.30	$23.30
Purchase #7	$19.49	10.108%	$21.46	$21.46	$21.45	$21.50
7 purchase totals =	$474.46		$510.7247	$510.72	$510.70	$510.80