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	$37.58	9.404%	$41.114	$41.11	$41.10	$41.10
Purchase #2	$82.33	8.827%	$89.5973	$89.60	$89.60	$89.60
Purchase #3	$169.36	10.685%	$187.4561	$187.46	$187.45	$187.50
Purchase #4	$188.83	5.637%	$199.4743	$199.47	$199.45	$199.50
Purchase #5	$64.27	4.269%	$67.0137	$67.01	$67.00	$67.00
Purchase #6	$145.95	12.416%	$164.0712	$164.07	$164.05	$164.10
Purchase #7	$238.62	9.198%	$260.5683	$260.57	$260.55	$260.60
7 purchase totals =	$926.94		$1,009.2949	$1,009.29	$1,009.20	$1,009.40