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	$199.87	7.125%	$214.1107	$214.11	$214.10	$214.10
Purchase #2	$209.92	13.337%	$237.917	$237.92	$237.90	$237.90
Purchase #3	$39.28	6.783%	$41.9444	$41.94	$41.95	$41.90
Purchase #4	$114.62	7.763%	$123.518	$123.52	$123.50	$123.50
Purchase #5	$223.39	4.354%	$233.1164	$233.12	$233.10	$233.10
Purchase #6	$85.59	13.299%	$96.9726	$96.97	$96.95	$97.00
Purchase #7	$83.58	6.566%	$89.0679	$89.07	$89.05	$89.10
7 purchase totals =	$956.25		$1,036.6470	$1,036.65	$1,036.55	$1,036.60