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	$164.84	13.733%	$187.4775	$187.48	$187.50	$187.50
Purchase #2	$59.74	13.576%	$67.8503	$67.85	$67.85	$67.90
Purchase #3	$10.34	13.146%	$11.6993	$11.70	$11.70	$11.70
Purchase #4	$240.57	13.513%	$273.0782	$273.08	$273.10	$273.10
Purchase #5	$33.74	6.582%	$35.9608	$35.96	$35.95	$36.00
Purchase #6	$245.91	7.725%	$264.9065	$264.91	$264.90	$264.90
Purchase #7	$185.65	5.722%	$196.2729	$196.27	$196.25	$196.30
7 purchase totals =	$940.79		$1,037.2455	$1,037.25	$1,037.25	$1,037.40