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	$233.86	11.528%	$260.8194	$260.82	$260.80	$260.80
Purchase #2	$131.53	9.775%	$144.3871	$144.39	$144.40	$144.40
Purchase #3	$246.47	13.344%	$279.359	$279.36	$279.35	$279.40
Purchase #4	$84.93	13.673%	$96.5425	$96.54	$96.55	$96.50
Purchase #5	$206.39	6.141%	$219.0644	$219.06	$219.05	$219.10
Purchase #6	$57.81	6.376%	$61.496	$61.50	$61.50	$61.50
Purchase #7	$35.26	5.664%	$37.2571	$37.26	$37.25	$37.30
7 purchase totals =	$996.25		$1,098.9255	$1,098.93	$1,098.90	$1,099.00