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	$239.31	10.531%	$264.5117	$264.51	$264.50	$264.50
Purchase #2	$57.72	3.316%	$59.634	$59.63	$59.65	$59.60
Purchase #3	$84.92	8.633%	$92.2511	$92.25	$92.25	$92.30
Purchase #4	$61.59	12.706%	$69.4156	$69.42	$69.40	$69.40
Purchase #5	$154.98	5.187%	$163.0188	$163.02	$163.00	$163.00
Purchase #6	$209.91	4.744%	$219.8681	$219.87	$219.85	$219.90
Purchase #7	$99.29	12.730%	$111.9296	$111.93	$111.95	$111.90
7 purchase totals =	$907.72		$980.6289	$980.63	$980.60	$980.60