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	$154.62	7.717%	$166.552	$166.55	$166.55	$166.60
Purchase #2	$172.77	4.638%	$180.7831	$180.78	$180.80	$180.80
Purchase #3	$31.53	5.422%	$33.2396	$33.24	$33.25	$33.20
Purchase #4	$158.59	6.779%	$169.3408	$169.34	$169.35	$169.30
Purchase #5	$149.39	4.150%	$155.5897	$155.59	$155.60	$155.60
Purchase #6	$60.96	3.731%	$63.2344	$63.23	$63.25	$63.20
Purchase #7	$137.86	5.736%	$145.7676	$145.77	$145.75	$145.80
7 purchase totals =	$865.72		$914.5072	$914.50	$914.55	$914.50