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	$156.94	6.844%	$167.681	$167.68	$167.70	$167.70
Purchase #2	$182.51	9.764%	$200.3303	$200.33	$200.35	$200.30
Purchase #3	$173.36	6.511%	$184.6475	$184.65	$184.65	$184.60
Purchase #4	$78.40	13.711%	$89.1494	$89.15	$89.15	$89.10
Purchase #5	$171.87	13.189%	$194.5379	$194.54	$194.55	$194.50
Purchase #6	$191.46	11.840%	$214.1289	$214.13	$214.15	$214.10
Purchase #7	$72.39	7.184%	$77.5905	$77.59	$77.60	$77.60
7 purchase totals =	$1,026.93		$1,128.0655	$1,128.07	$1,128.15	$1,127.90