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	$72.25	13.441%	$81.9611	$81.96	$81.95	$82.00
Purchase #2	$246.31	8.223%	$266.5641	$266.56	$266.55	$266.60
Purchase #3	$167.46	11.229%	$186.2641	$186.26	$186.25	$186.30
Purchase #4	$59.76	11.507%	$66.6366	$66.64	$66.65	$66.60
Purchase #5	$59.38	7.112%	$63.6031	$63.60	$63.60	$63.60
Purchase #6	$41.52	8.736%	$45.1472	$45.15	$45.15	$45.10
Purchase #7	$159.39	13.187%	$180.4088	$180.41	$180.40	$180.40
7 purchase totals =	$806.07		$890.5850	$890.58	$890.55	$890.60