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	$20.48	7.735%	$22.0641	$22.06	$22.05	$22.10
Purchase #2	$180.87	4.801%	$189.5536	$189.55	$189.55	$189.60
Purchase #3	$81.39	5.507%	$85.8721	$85.87	$85.85	$85.90
Purchase #4	$40.31	7.661%	$43.3981	$43.40	$43.40	$43.40
Purchase #5	$179.50	6.761%	$191.636	$191.64	$191.65	$191.60
Purchase #6	$95.51	4.127%	$99.4517	$99.45	$99.45	$99.50
Purchase #7	$53.93	8.104%	$58.3005	$58.30	$58.30	$58.30
7 purchase totals =	$651.99		$690.2761	$690.27	$690.25	$690.40