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	$32.86	6.683%	$35.056	$35.06	$35.05	$35.10
Purchase #2	$17.50	5.341%	$18.4347	$18.43	$18.45	$18.40
Purchase #3	$179.27	6.792%	$191.446	$191.45	$191.45	$191.40
Purchase #4	$187.92	5.601%	$198.4454	$198.45	$198.45	$198.40
Purchase #5	$96.75	6.260%	$102.8066	$102.81	$102.80	$102.80
Purchase #6	$184.37	6.437%	$196.2379	$196.24	$196.25	$196.20
Purchase #7	$91.39	11.112%	$101.5453	$101.55	$101.55	$101.50
7 purchase totals =	$790.06		$843.9719	$843.99	$844.00	$843.80