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	$166.36	11.727%	$185.869	$185.87	$185.85	$185.90
Purchase #2	$64.89	11.655%	$72.4529	$72.45	$72.45	$72.50
Purchase #3	$40.25	7.485%	$43.2627	$43.26	$43.25	$43.30
Purchase #4	$45.26	12.200%	$50.7817	$50.78	$50.80	$50.80
Purchase #5	$242.86	11.760%	$271.4203	$271.42	$271.40	$271.40
Purchase #6	$187.86	11.534%	$209.5278	$209.53	$209.55	$209.50
Purchase #7	$167.61	3.830%	$174.0295	$174.03	$174.05	$174.00
7 purchase totals =	$915.09		$1,007.3439	$1,007.34	$1,007.35	$1,007.40