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	$116.40	9.661%	$127.6454	$127.65	$127.65	$127.60
Purchase #2	$130.75	4.482%	$136.6102	$136.61	$136.60	$136.60
Purchase #3	$16.63	6.675%	$17.7401	$17.74	$17.75	$17.70
Purchase #4	$55.44	12.224%	$62.217	$62.22	$62.20	$62.20
Purchase #5	$211.78	3.333%	$218.8386	$218.84	$218.85	$218.80
Purchase #6	$113.40	12.347%	$127.4015	$127.40	$127.40	$127.40
Purchase #7	$178.58	12.144%	$200.2668	$200.27	$200.25	$200.30
7 purchase totals =	$822.98		$890.7196	$890.73	$890.70	$890.60