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	$176.55	5.213%	$185.7536	$185.75	$185.75	$185.80
Purchase #2	$239.89	13.648%	$272.6302	$272.63	$272.65	$272.60
Purchase #3	$89.42	11.429%	$99.6398	$99.64	$99.65	$99.60
Purchase #4	$65.50	6.259%	$69.5996	$69.60	$69.60	$69.60
Purchase #5	$180.56	7.747%	$194.548	$194.55	$194.55	$194.50
Purchase #6	$142.61	9.661%	$156.3876	$156.39	$156.40	$156.40
Purchase #7	$85.30	4.712%	$89.3193	$89.32	$89.30	$89.30
7 purchase totals =	$979.83		$1,067.8781	$1,067.88	$1,067.90	$1,067.80