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	$148.77	10.288%	$164.0755	$164.08	$164.10	$164.10
Purchase #2	$198.53	8.583%	$215.5698	$215.57	$215.55	$215.60
Purchase #3	$94.37	6.781%	$100.7692	$100.77	$100.75	$100.80
Purchase #4	$10.80	11.796%	$12.074	$12.07	$12.05	$12.10
Purchase #5	$45.92	10.178%	$50.5937	$50.59	$50.60	$50.60
Purchase #6	$214.30	11.128%	$238.1473	$238.15	$238.15	$238.10
Purchase #7	$212.33	7.832%	$228.9597	$228.96	$228.95	$229.00
7 purchase totals =	$925.02		$1,010.1892	$1,010.19	$1,010.15	$1,010.30