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	$207.44	11.290%	$230.86	$230.86	$230.85	$230.90
Purchase #2	$194.39	10.791%	$215.3666	$215.37	$215.35	$215.40
Purchase #3	$118.59	3.719%	$123.0004	$123.00	$123.00	$123.00
Purchase #4	$133.86	10.614%	$148.0679	$148.07	$148.05	$148.10
Purchase #5	$150.86	13.781%	$171.65	$171.65	$171.65	$171.70
Purchase #6	$94.74	10.718%	$104.8942	$104.89	$104.90	$104.90
Purchase #7	$81.49	3.687%	$84.4945	$84.49	$84.50	$84.50
7 purchase totals =	$981.37		$1,078.3336	$1,078.33	$1,078.30	$1,078.50