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	$78.29	11.778%	$87.511	$87.51	$87.50	$87.50
Purchase #2	$82.50	3.654%	$85.5146	$85.51	$85.50	$85.50
Purchase #3	$99.51	7.624%	$107.0966	$107.10	$107.10	$107.10
Purchase #4	$163.79	13.186%	$185.3873	$185.39	$185.40	$185.40
Purchase #5	$196.59	4.564%	$205.5624	$205.56	$205.55	$205.60
Purchase #6	$226.83	5.127%	$238.4596	$238.46	$238.45	$238.50
Purchase #7	$152.70	6.608%	$162.7904	$162.79	$162.80	$162.80
7 purchase totals =	$1,000.21		$1,072.3219	$1,072.32	$1,072.30	$1,072.40