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	$54.33	9.706%	$59.6033	$59.60	$59.60	$59.60
Purchase #2	$104.88	9.353%	$114.6894	$114.69	$114.70	$114.70
Purchase #3	$68.31	3.764%	$70.8812	$70.88	$70.90	$70.90
Purchase #4	$54.76	12.266%	$61.4769	$61.48	$61.50	$61.50
Purchase #5	$239.41	11.194%	$266.2096	$266.21	$266.20	$266.20
Purchase #6	$238.40	7.651%	$256.64	$256.64	$256.65	$256.60
Purchase #7	$238.27	11.674%	$266.0856	$266.09	$266.10	$266.10
7 purchase totals =	$998.36		$1,095.5860	$1,095.59	$1,095.65	$1,095.60