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	$96.40	5.325%	$101.5333	$101.53	$101.55	$101.50
Purchase #2	$89.59	9.276%	$97.9004	$97.90	$97.90	$97.90
Purchase #3	$41.84	11.190%	$46.5219	$46.52	$46.50	$46.50
Purchase #4	$228.29	4.566%	$238.7137	$238.71	$238.70	$238.70
Purchase #5	$37.27	7.380%	$40.0205	$40.02	$40.00	$40.00
Purchase #6	$35.34	5.476%	$37.2752	$37.28	$37.30	$37.30
Purchase #7	$27.65	5.345%	$29.1279	$29.13	$29.15	$29.10
7 purchase totals =	$556.38		$591.0929	$591.09	$591.10	$591.00