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	$94.33	6.440%	$100.4049	$100.40	$100.40	$100.40
Purchase #2	$236.86	7.287%	$254.12	$254.12	$254.10	$254.10
Purchase #3	$54.86	5.354%	$57.7972	$57.80	$57.80	$57.80
Purchase #4	$174.73	5.791%	$184.8486	$184.85	$184.85	$184.80
Purchase #5	$148.68	13.298%	$168.4515	$168.45	$168.45	$168.50
Purchase #6	$186.96	10.368%	$206.344	$206.34	$206.35	$206.30
Purchase #7	$133.97	9.451%	$146.6315	$146.63	$146.65	$146.60
7 purchase totals =	$1,030.39		$1,118.5977	$1,118.59	$1,118.60	$1,118.50